Augmented and virtual reality display systems with shared display for left and right eyes

ABSTRACT

A wearable display system includes a light projection system having one or more emissive microdisplays, e.g., micro-LED displays. The light projection system projects time-multiplexed left-eye and right-eye images, which pass through an optical router having a polarizer and a switchable polarization rotator. The optical router is synchronized with the generation of images by the light projection system to impart a first polarization to left-eye images and a second different polarization to right-eye images. Light of the first polarization is incoupled into an eyepiece having one or more waveguides for outputting light to one of the left and right eyes, while light of the second polarization may be incoupled into another eyepiece having one or more waveguides for outputting light to the other of the left and right eyes. Each eyepiece may output incoupled light with variable amounts of wavefront divergence, to elicit different accommodation responses from the user&#39;s eyes.

PRIORITY CLAIM

This application claims priority from: U.S. Provisional Application No.62/858,927 filed on Jun. 7, 2019 and titled “AUGMENTED AND VIRTUALREALITY DISPLAY SYSTEMS WITH SHARED DISPLAY FOR LEFT AND RIGHT EYES”;U.S. Provisional Application No. 62/800,363 filed on Feb. 1, 2019 andtitled “VIRTUAL AND AUGMENTED REALITY DISPLAY SYSTEMS WITH EMISSIVEMICRO-DISPLAYS”; U.S. Provisional Application No. 62/911,018 filed onOct. 4, 2019 and titled “AUGMENTED AND VIRTUAL REALITY DISPLAY SYSTEMSWITH SHARED DISPLAY FOR LEFT AND RIGHT EYES”; and U.S. ProvisionalApplication No. 62/786,199 filed on Dec. 28, 2018 and titled “LOWMOTION-TO-PHOTON LATENCY ARCHITECTURE FOR AUGMENTED AND VIRTUAL REALITYDISPLAY SYSTEMS”. The above-noted applications are hereby incorporatedby reference herein in their entireties.

INCORPORATION BY REFERENCE

This application incorporates by reference the entireties of each of thefollowing: U.S. application Ser. No. 14/555,585 filed on Nov. 27, 2014,published on Jul. 23, 2015 as U.S. Publication No. 2015/0205126; U.S.application Ser. No. 14/690,401 filed on Apr. 18, 2015, published onOct. 22, 2015 as U.S. Publication No. 2015/0302652; U.S. applicationSer. No. 14/212,961 filed on Mar. 14, 2014, now U.S. Pat. No. 9,417,452issued on Aug. 16, 2016; U.S. application Ser. No. 14/331,218 filed onJul. 14, 2014, published on Oct. 29, 2015 as U.S. Publication No.2015/0309263; U.S. Patent App. Pub. No. 2018/0061121, published Mar. 1,2018; U.S. patent application Ser. No. 16/221,065, filed Dec. 14, 2018;U.S. Patent App. Pub. No. 2018/0275410, published Sep. 27, 2018; U.S.Provisional Application No. 62/786,199, filed Dec. 28, 2018; and U.S.application Ser. No. 16/221,359, filed on Dec. 14, 2018; U.S.Provisional Application No. 62/702,707, filed on Jul. 24, 2018; and U.S.application Ser. No. 15/481,255, filed Apr. 6, 2017.

BACKGROUND Field

The present disclosure relates to display systems and, moreparticularly, to augmented and virtual reality display systems.

Description of the Related Art

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, in which digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves the presentation of digital or virtual imageinformation without transparency to other actual real-world visualinput; an augmented reality, or “AR”, scenario typically involvespresentation of digital or virtual image information as an augmentationto visualization of the actual world around the user. A mixed reality,or “MR”, scenario is a type of AR scenario and typically involvesvirtual objects that are integrated into, and responsive to, the naturalworld. For example, an MR scenario may include AR image content thatappears to be blocked by or is otherwise perceived to interact withobjects in the real world.

Referring to FIG. 1, an augmented reality scene 10 is depicted. The userof an AR technology sees a real-world park-like setting 20 featuringpeople, trees, buildings in the background, and a concrete platform 30.The user also perceives that he/she “sees” “virtual content” such as arobot statue 40 standing upon the real-world platform 30, and a flyingcartoon-like avatar character 50 which seems to be a personification ofa bumble bee. These elements 50, 40 are “virtual” in that they do notexist in the real world. Because the human visual perception system iscomplex, it is challenging to produce AR technology that facilitates acomfortable, natural-feeling, rich presentation of virtual imageelements amongst other virtual or real-world imagery elements.

SUMMARY

In some embodiments, a head-mounted display system comprises ahead-mountable frame, a light projection system, a left eyepiecesupported by the frame, a right eyepiece supported by the frame, and anoptical router. The light projection system comprises an emissivemicro-display and is configured to output image light comprisingleft-eye image light for forming left-eye images time-multiplexed withright-eye image light for forming right-eye images. The optical routeris configured to receive the image light from the light projectionsystem, and provide, at different times, the left-eye image light to theleft eyepiece and the right-eye image light to the right eyepiece.

Some additional examples of embodiments are provided below.

Example 1. A head-mounted display system comprising:

-   -   a head-mountable frame;    -   a light projection system comprising an emissive micro-display,        wherein the light projection system is configured to output        image light comprising left-eye image light for forming left-eye        images time-multiplexed with right-eye image light for forming        right-eye images;    -   a left eyepiece supported by the frame;    -   a right eyepiece supported by the frame; and    -   an optical router configured to:        -   receive the image light from the light projection system,            and        -   provide, at different times, the left-eye image light to the            left eyepiece and the right-eye image light to the right            eyepiece.

Example 2. The head-mounted display system of Example 1, wherein theoptical router comprises:

-   -   a polarizer configured to receive the image light and to output        the image light with a first polarization state; and    -   a switchable polarization rotator configured to receive the        image light with the first polarization state and to selectively        change a polarization state of the received image light to a        second polarization state.

Example 3. The head-mounted display system of Example 2, wherein theelectrically-switchable polarization rotator comprises a switchablehalf-wave plate (HWP).

Example 4. The head-mounted display system of Example 2, furthercomprising control electronics configured to synchronize:

-   -   generation of left-eye image images by the light projection        system and routing of the left-eye image light to the left        eyepiece by the optical router; and    -   generation of the right-eye images by the light projection        system and routing of the right-eye image light to the right        eyepiece by the optical router,    -   wherein the electrically-switchable polarization rotator is        synchronized, by the control electronics, with the light        projection system to output left-eye image light with a first        polarization state and to output right-eye image light with a        second polarization different from the first polarization state.

Example 5. The head-mounted display system of Example 2, wherein theoptical router further comprises a polarization-sensitive reflectorconfigured to receive the image light from the switchable polarizationrotator,

-   -   wherein the polarization-sensitive reflector is configured to        reflect image light having the first polarization state and        transmit image light having the second polarization state.

Example 6. The head-mounted display system of Example 5, wherein thepolarization-sensitive reflector is configured to:

-   -   direct left-eye image light having one of the first and second        polarization states towards the left eyepiece; and    -   direct right-eye image light having the other of the first and        second polarization states towards the right eyepiece.

Example 7. The head-mounted display system of Example 5, wherein thepolarization-sensitive reflector comprises a polarization beam splitter.

Example 8. The head-mounted display system of Example 1, wherein theleft eyepiece comprises one or more left-eye waveguides forming aleft-eye waveguide assembly, each left-eye waveguide comprising:

-   -   a left-eye in-coupling optical element configured to in-couple        image light into the left-eye waveguide; and    -   a left-eye out-coupling optical element configured to out-couple        in-coupled image light out of the left-eye waveguide, and    -   the right eyepiece comprises one or more right-eye waveguides        forming a right-eye waveguide assembly, each right-eye waveguide        comprising:        -   a right-eye in-coupling optical element configured to            in-couple image light into the right-eye waveguide; and        -   a right-eye out-coupling optical element configured to            out-couple in-coupled image light out of the right-eye            waveguide.

Example 9. The head-mounted display system of Example 8, wherein theleft-eye waveguide assembly is configured to output the in-coupled lightwith variable amounts of wavefront divergence corresponding to aplurality of depth planes and wherein the right-eye waveguide assemblyis configured to output the out-coupled light with variable amounts ofwavefront divergence corresponding to the plurality of depth planes.

Example 10. The head-mounted display system of Example 8, wherein theleft-eye waveguide assembly comprises a first stack of waveguides,wherein the right-eye waveguide assembly comprises a second stack ofwaveguides, wherein the light projection system is configured to outputlight of a plurality of component colors, wherein each of the left-eyeand right-eye waveguide assemblies comprises at least one dedicatedwaveguide for light of each component color.

Example 11. The head-mounted display system of Example 1, wherein theleft eyepiece comprises one or more left-eye waveguides, each left-eyewaveguide comprising:

-   -   a left-eye polarization-sensitive in-coupling optical element        configured to in-couple light having the first polarization        state into the left-eye waveguide; and    -   a left-eye out-coupling optical element configured to out-couple        in-coupled light out of the left-eye waveguide.

Example 12. The head-mounted display system of Example 11, wherein theright eyepiece comprises:

one or more right-eye waveguides, each right-eye waveguide comprising:

-   -   a right-eye polarization-sensitive in-coupling optical element        configured to in-couple light having the second polarization        state into the right-eye waveguide; and    -   a right-eye out-coupling optical element configured to        out-couple in-coupled light out of the right-eye waveguide.

Example 13. The head-mounted display of Example 12, wherein the left-eyepolarization-sensitive in-coupling optical element and the right-eyepolarization-sensitive in-coupling optical element are disposed in asame image light path.

Example 14. The head-mounted display of Example 13, further comprising acleanup polarizer disposed between the left-eye polarization-sensitivein-coupling optical element and the right-eye polarization-sensitivein-coupling optical element, wherein the cleanup polarizer is configuredto:

block light not having a polarization for which the downstreampolarization-sensitive in-coupling optical element is configuredsensitive.

Example 15. The head-mounted display system of Example 1, wherein theemissive micro-display comprises a micro-LED display.

Example 16. The head-mounted display system of Example 1, furthercomprising a plurality of emissive micro-displays, wherein eachmicro-LED display is a monochromatic and configured to emit light of acomponent color.

Example 17. The head-mounted display system of Example 16, furthercomprising an X-cube prism, wherein each of the emissive micro-LEDdisplays face a different side of the X-cube prism.

Example 18. The head-mounted display system of Example 17, wherein eachmicro-LED display comprises an array of light emitters, furthercomprising a plurality of arrays of light collimators, wherein eachmicro-display has an associated array of light collimators, and whereineach array of light collimators is configured to capture and reduce anangular emission profile of light from the micro-display.

Example 19. The head-mounted display system of Example 18, wherein thelight collimators comprise micro-lenses.

Example 20. The head-mounted display system of Example 18, wherein thelight collimators comprise nano-lenses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of augmented reality (AR) through an ARdevice.

FIG. 2 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIGS. 3A-3C illustrate relationships between radius of curvature andfocal radius.

FIG. 4A illustrates a representation of the accommodation-vergenceresponse of the human visual system.

FIG. 4B illustrates examples of different accommodative states andvergence states of a pair of eyes of the user.

FIG. 4C illustrates an example of a representation of a top-down view ofa user viewing content via a display system.

FIG. 4D illustrates another example of a representation of a top-downview of a user viewing content via a display system.

FIG. 5 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user.

FIG. 7 illustrates an example of exit beams outputted by a waveguide.

FIG. 8 illustrates an example of a stacked eyepiece in which each depthplane includes images formed using multiple different component colors.

FIG. 9A illustrates a cross-sectional side view of an example of a setof stacked waveguides that each includes an in-coupling optical element.

FIG. 9B illustrates a perspective view of an example of the plurality ofstacked waveguides of FIG. 9A.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B.

FIG. 9D illustrates a top-down plan view of another example of aplurality of stacked waveguides.

FIG. 9E illustrates an example of wearable display system.

FIG. 10 illustrates an example of a wearable display system with a lightprojection system having a spatial light modulator and a separate lightsource.

FIG. 11A illustrates an example of a wearable display system with alight projection system having multiple emissive micro-displays.

FIG. 11B illustrates an example of an emissive micro-display with anarray of light emitters.

FIG. 12 illustrates another example of a wearable display system with alight projection system having multiple emissive micro-displays andassociated light redirecting structures.

FIG. 13A illustrates an example of a side-view of a wearable displaysystem with a light projection system having multiple emissivemicro-displays and an eyepiece having waveguides with overlapping andlaterally-shifted light in-coupling optical elements.

FIG. 13B illustrates another example of a wearable display system with alight projection system having multiple emissive micro-displaysconfigured to direct light to a single light in-coupling area of aneyepiece.

FIG. 14 illustrates an example of a wearable display system with asingle emissive micro-display.

FIG. 15 illustrates a side view of an example of an eyepiece having astack of waveguides with overlapping in-coupling optical elements.

FIG. 16 illustrates a side view of an example of a stack of waveguideswith color filters for mitigating ghosting or crosstalk betweenwaveguides.

FIG. 17 illustrates an example of a top-down view of the eyepieces ofFIGS. 15 and 16.

FIG. 18 illustrates another example of a top-down view of the eyepiecesof FIGS. 15 and 16.

FIG. 19A illustrates a side view of an example of an eyepiece having astack of waveguides with overlapping and laterally-shifted in-couplingoptical elements.

FIG. 19B illustrates a side view of an example of the eyepiece of FIG.19A with color filters for mitigating ghosting or crosstalk betweenwaveguides.

FIG. 20A illustrates an example of a top-down view of the eyepieces ofFIGS. 19A and 19B.

FIG. 20B illustrates another example of a top-down view of the eyepiecesof FIGS. 19A and 19B.

FIG. 21 illustrates a side view of an example of re-bounce in awaveguide.

FIGS. 22A-22C illustrate examples of top-down views of an eyepiecehaving in-coupling optical elements configured to reduce re-bounce.

FIGS. 23A-23C illustrate additional examples of top-down views of aneyepiece having in-coupling optical elements configured to reducere-bounce.

FIG. 24A illustrates an example of angular emission profiles of lightemitted by individual light emitters of an emissive micro-display, andlight captured by projection optics.

FIG. 24B illustrates an example of the narrowing of angular emissionprofiles using an array of light collimators.

FIG. 25A illustrates an example of a side view of an array of taperedreflective wells for directing light to projection optics.

FIG. 25B illustrates an example of a side view of an asymmetric taperedreflective well.

FIGS. 26A-26C illustrate examples of differences in light paths forlight emitters at different positions relative to center lines ofoverlying lens.

FIG. 27 illustrates an example of a side view of individual lightemitters of an emissive micro-display with an overlying nano-lens array.

FIG. 28 is a perspective view of an example of the emissivemicro-display of FIG. 27.

FIG. 29 illustrates an example of a wearable display system with thefull-color emissive micro-display of FIG. 28.

FIG. 30A illustrates an example of a wearable display system with anemissive micro-display and an associated array of light collimators.

FIG. 30B illustrates an example of a light projection system withmultiple emissive micro-displays, each with an associated array of lightcollimators.

FIG. 30C illustrates an example of a wearable display system withmultiple emissive micro-displays, each with an associated array of lightcollimators.

FIGS. 31A and 31B illustrate examples of waveguide assemblies havingvariable focus elements for varying the wavefront divergence of light toa viewer.

FIG. 32 illustrates an example of a wearable display system with a lightprojection system having one or more emissive micro-displays, and anoptical router for selectively directing light to left and righteyepieces.

FIG. 33 illustrates an example of a wearable display system having anoptical router that includes a polarization-sensitive reflectivestructure for selectively directing images to left and right eyepieces.

FIG. 34 illustrates an example of a wearable display system with anoptical router that switches polarization states of incident imagelight, and left and right eyepieces having in-coupling optical elementsthat selectively in-couple light of different polarization states.

DETAILED DESCRIPTION

As described herein, AR and/or VR systems may display virtual content toa user, or viewer. This content may be displayed on a head-mounteddisplay, e.g., as part of eyewear, that projects image information tothe user's eyes. In addition, where the system is an AR system, thedisplay may also transmit light from a surrounding environment to theuser's eyes, to allow a view of the surrounding environment. As usedherein, it will be appreciated that a “head-mounted” or “head mountable”display is a display that may be mounted on the head of the user orviewer.

Many head-mounted display systems utilize transmissive or reflectivespatial light modulators to form images that are presented to the user.A light source emits light, which is directed to the spatial lightmodulator, which then modulates the light, which is then directed to theuser. Lens structures may be provided between the light source and thespatial light modulator to focus light from the light source onto thespatial light modulator. Undesirably, the light source and relatedoptics may add bulkiness and weight to the display system. Thisbulkiness or weight may be compounded since different images may bepresented to the left and right eyes of the user and, as such, each eyemay have a dedicated associated light source and spatial lightmodulator. The bulk and weight of the associate light sources andassociated spatial light modulators may adversely impact the comfort ofthe display system and the ability to wear the system for longdurations.

In addition, it has been found that the frame rate limitations of somedisplay systems may cause viewing discomfort. Some display systems usespatial light modulators to form images. Many spatial light modulatorsutilize movement of optical elements to modulate the intensity of lightoutputted by the spatial light modulator, to thereby form the images.For example, MEMS-based spatial light modulators may utilize movingmirrors to modulate incident light, while LCoS-based displays mayutilize the movement of liquid crystal molecules to modulate light.Other AR or VR systems may utilize scanning-fiber displays, in which theend of an optical fiber physically moves across an area while outputtinglight. The light outputted by the optical fiber is timed with theposition of the end of the fiber, thereby effectively mimicking pixelsat different locations, and thereby forming images. The requirement thatthe optical fibers, mirrors, and liquid crystal molecules physicallymove limits the speed at which individual pixels may change states andalso constrains the frame rate of displays using these optical elements.

Such limitations may cause viewing discomfort due to, e.g., motion blurand/or mismatches between the orientation of the user's head and thedisplayed image. For example, there may be latency in the detection ofthe orientation of the user's head and the presentation of imagesconsistent with that orientation. In the timespan between detecting theorientation and presenting an image to the user, the user's head mayhave moved. The presented image, however, may correspond to a view of anobject from a different orientation. Such a mismatch between theorientation of the user's head and the presented image may causediscomfort in the user (e.g., nausea).

In addition, scanning-fiber displays may present other undesirableoptical artifacts due to, e.g., the small cross-section of the fibers,which requires the use of a high-intensity light source to form imagesof desirable apparent brightness. Suitable high-intensity light sourcesinclude lasers, which output coherent light. Undesirably, the use ofcoherent light may cause optical artifacts.

Advantageously, display systems utilizing emissive micro-displays asdescribed herein may allow for a low-weight and compact form factor, andmay also provide a high frame rate and low motion blur. Preferably, themicro-displays are emissive micro-displays, which provide advantages forhigh brightness and high pixel density. In some embodiments, theemissive micro-displays are micro-LED displays. In some otherembodiments, the emissive micro-displays are micro-OLED displays. Insome embodiments, the emissive micro-displays comprise arrays of lightemitters having a pitch of, e.g., less than 10 μm, less than 8 μm, lessthan 6 μm, less than 5 μm, or less than 2 μm, including 1-5 μm, and anemitter size of 2 μm or less, 1.7 μm or less, or 1.3 μm or less. In someembodiments, the emitter size is within a range having an upper limit ofthe above-noted sizes and a lower limit of 1 μm. In some embodiments,the ratio of emitter size to pitch is 1:1 to 1:5, 1:2 to 1:4, or 1:2 to1:3, which may have advantages for individual control of emitters andefficient utilization of emitted light by eyepieces, as discussedfurther herein.

In some embodiments, a plurality of emissive micro-displays may beutilized to form images for a head-mounted display system. The lightcontaining the image information for forming these images may bereferred to as image light. It will be appreciated that image light mayvary in, e.g., wavelength, intensity, polarization, etc. The emissivemicro-displays output image light to an eyepiece, which then relays thelight to an eye of the user.

In some embodiments, a head mounted display system may include left andright eyepieces for relaying image light to the user's left and righteyes, respectively. The head mounted display system may also include alight projection system and an optical router for routing image light toan appropriate one of the left and right eyepieces. The light projectionsystem may be configured to generate distinct images (e.g., imageframes) for both left and right eyepieces of the display system, and theoptical router may be configured to direct the left-eye and right-eyeimage frames to the corresponding one of the left and right eyepieces.In some embodiments, the light projection system utilizes an emissivemicro-display, which has advantages for high frame rates, whichfacilitate the use of a common light projection system for both the leftand right eyepieces.

In some embodiments, the light projection system may be configured totime-multiplex left and right eyepiece image frames and the opticalrouter may be configured to route the left image frames to the lefteyepiece and the right image frames to the right eyepiece. In someembodiments, the light projection system may utilize one or moreemissive micro-displays with a frame rate of 120 Hz or more, whichadvantageously may provide left-eye image frames at frame rates of 60 Hzor more to a left eyepiece, while also providing right-eye image framesat frame rates of 60 Hz or more to a right eyepiece. The micro-displaysmay interleave in time (e.g., time-multiplex) the left-eye and right-eyeimage frames, which may also be referred to as left-eye and right-eyeimages. For example, the micro-displays may alternate between generatinga left-eye image frame (that is, an image frame of content intended forthe left-eye) that is routed to a left eyepiece and a right-eye imageframe (that is, an image frame of content intended for the right-eye)that is routed to a right eyepiece. The optical router may de-multiplexthe left-eye and right-eye image frames by routing left-eye image framesto the left eyepiece, and right-eye image frames to the right eyepiece.

In some embodiments, the optical router may be an electricallyswitchable device which provides selectable switching of the path of thelight being outputted by the router and/or which provides selectableswitching of a property of the light to change a way that the lightinteracts with (e.g. propagates through) subsequent downstreamstructures. In some embodiments, routing light via the optical router toone of the left or right eyepieces may include changing a polarizationstate of the light.

In some embodiments, the optical router may be a mechanically switchabledevice, such as a moveable mirror that switches between: a firstorientation that reflects light to one of the right or left eyepieces,and a second orientation that reflects light to the other of the rightor left eyepieces. For example, the optical router may comprise a MEMSmirror or a scanning mirror.

For example, a first reflector that selectively reflects light of aparticular polarization state may be utilized to reflect light of afirst polarization state towards a corresponding eyepiece, whiletransmitting light of a second polarization state to a second reflector,which then reflects the remaining light to the other eyepiece. In someembodiments, the second reflector may selectively reflect light of thesecond polarization state to the other eyepiece.

In some embodiments, the left and right eyepieces may have in-couplingoptical elements that overlap (e.g., are both in a common path of lightfrom the light projection system). The optical router routes light tothe appropriate eyepiece by changing a polarization state of the outputimage light so that, for example, left eyepiece image frames are formedby light with the appropriate polarization state to be in-coupled by thein-coupling optical elements of the left eyepiece, and right eyepieceimage frames are formed by light with the appropriate polarization stateto be in-coupled by the in-coupling optical elements of the righteyepiece.

Thus, in some embodiments, the left and right eyepieces share a commonlight projection system, which may reduce bulkiness and weight relativeto using dedicated light projection systems for each of the left andright eyepieces. In addition, the light projection system preferablyutilizes one or more emissive micro-displays, which further providesadvantages (e.g., for reducing bulkiness and weight), as discussedherein.

In some embodiments, a plurality of emissive micro-displays may beutilized and positioned at different sides of an optical combiner, e.g.,an X-cube prism or dichroic X-cube. The X-cube prism receives light raysfrom different micro-displays on different faces of the cube and outputsthe light rays from the same face of the cube. The outputted light maybe directed towards projection optics, which is configured to convergeor focus the image light onto the eyepiece.

In some embodiments, the plurality of emissive micro-displays comprisesmonochrome micro-displays, which are configured to output light of asingle component color. Combining various component colors forms a fullcolor image. In some other embodiments, one or more of the emissivemicro-displays may have sub-pixels configured to emit light of two ormore, but not all, component colors utilized by the display system. Forexample, a single emissive micro-display may have sub-pixels which emitlight of the colors blue and green, while a separate emissivemicro-display on a different face of the X-cube may have pixelsconfigured to emit red light. In some embodiments, the plurality ofmicro-displays are each full-color displays comprising, e.g., pixelsformed of multiple sub-pixels configured to emit light of differentcomponent colors. Advantageously, combining the light of multiplefull-color micro-displays may increase display brightness and dynamicrange.

It will be appreciated that the emissive micro-displays may comprisearrays of light emitters. The light emitters may emit light with aLambertian angular emission profile. Undesirably, such an angularremission profile may “waste” light, since only a small portion of theemitted light may ultimately be incident on the eyepiece. In someembodiments, light collimators may be utilized to narrow the angularemission profile of light emitted by the light emitters. As used herein,a light collimator is an optical structure which narrows the angularemission profile of incident light; that is, the light collimatorreceives light from an associated light emitter with a relatively wideinitial angular emission profile and outputs that light with a narrowerangular emission profile than the wide initial angular emission profile.In some embodiments, the rays of light exiting the light collimator aremore parallel than the rays of light received by the light collimator,before being transmitted through and exiting the collimator. Examples oflight collimators include micro-lenses, nano-lenses, reflective wells,metasurfaces, and liquid crystal gratings. In some embodiments, thelight collimators may be configured to steer light to ultimatelyconverge on different laterally-shifted light-coupling optical elements.In some embodiments, each light emitter has a dedicated lightcollimator. The light collimators are preferably positioned directlyadjacent or contacting the light emitters, to capture a large proportionof the light emitted by the associated light emitters.

In some embodiments, a single emissive micro-display may be utilized todirect light to the eyepiece. For example, the single emissivemicro-display may be a full-color display comprising light emitters thatemit light of different component colors. In some embodiments, the lightemitters may form groups, which are localized in a common area, witheach group comprising light emitters which emit light of each componentcolor. In such embodiments, each group of light emitters may share acommon micro-lens. Advantageously, light of different colors fromdifferent light emitters take a different path through the micro-lens,which may be manifested in light of different component colors beingincident on different in-coupling optical elements of an eyepiece, asdiscussed herein.

In some embodiments, the full-color micro-display may comprise repeatinggroups of light emitters of the same component color. For instance, themicro-display may include rows of light emitters, with the lightemitters of each individual row configured to emit light of the samecolor. Thus, different rows may emit light of different componentcolors. In addition, the micro-display may have an associated array oflight collimators configured to direct light to a desired location on aneyepiece, e.g., to an associated in-coupling optical element.Advantageously, while the individual light emitters of such a full-colormicro-display may not be positioned to form a high-quality full-colorimage, as viewed directly on the micro-display, the lens arrayappropriately steers the light from the light emitters to the eyepiece,which combines monochrome images formed by light emitters of differentcolors, thereby forming a high-quality full-color image.

In some embodiments, the eyepiece receiving image light from themicro-displays may comprise a waveguide assembly. The area of awaveguide of the waveguide assembly on which the image light is incidentmay include in-coupling optical elements which in-couple incident imagelight, such that the light propagates through the waveguide by totalinternal reflection (TIR). In some embodiments, the waveguide assemblymay include a stack of waveguides, each of which has an associatedin-coupling optical element. Different in-coupling optical elements maybe configured to in-couple light of different colors, such thatdifferent waveguides may be configured to propagate light of differentcolors therein. The waveguides may include out-coupling opticalelements, which out-couple light propagating therein, such that theout-coupled light propagates towards the eye of the user. In some otherembodiments, the waveguide assembly may include a single waveguidehaving an associated in-coupling optical element configured to in-couplelight of different component colors.

In some embodiments, the in-coupling optical elements are laterallyshifted, as seen from the projection optics. Different in-couplingoptical elements may be configured to in-couple light of differentcolors. Preferably, image light of different colors take different pathsto the eyepiece and, thus, impinge upon different correspondingin-coupling optical elements.

In some other embodiments, other types of eyepieces or optics forrelaying image light to the eyes of the user may be utilized. Forexample, as discussed herein, the eyepiece may include one or morewaveguides which propagates image light therein by TIR. As anotherexample, the eyepiece may include a birdbath combiner comprising asemitransparent mirror that both directs image light to a viewer andallows a view of the ambient environment.

In some embodiments, the eyepiece may be configured to selectivelyoutput light with different amounts of wavefront divergence, to providevirtual content at a plurality of virtual depth planes (also referred tosimply as “depth planes” herein) perceived to be at different distancesaway from the user. For example, the eyepiece may comprise a pluralityof waveguides each having out-coupling optical elements with differentoptical power to output light with different amounts of wavefrontdivergence. In some other embodiments, a variable focus element may beprovided between the eyepiece and the user's eye. The variable focuselement may be configured to dynamically change optical power to providethe desired wavefront divergence for particular virtual content. In someembodiments, as an alternative to, or in addition to waveguide opticalstructures for providing optical power, the display systems may alsoinclude a plurality of lenses that provide or additionally provideoptical powers.

In addition to the compact form factor and high frame rates discussedabove, emissive micro-displays according to some embodiments may provideone of more of the following advantages. For example, the micro-displaysmay provide exceptionally small pixel pitches and high pixel density.The micro-displays may also provide high luminance and efficiency. Forexample, the light emitters of the emissive micro-displays may onlyconsume power to emit light when the light emitters are needed providecontent with luminance. This is in contrast to other displaytechnologies in which the light source may illuminate an entire panel ofpixels, whether or not some of those pixels are dark. Further, it willbe appreciated that the human visual system integrates received lightover time and the light emitters of emissive micro-displays, such asmicro-LEDs, have advantageously high duty cycles (e.g., including ashort activation period for a light emitter in a micro-display to risefrom an “off” to a full “on” state, and a correspondingly short time tofall from an “on” state to “off” state allow the light emitters to emitlight at the on level for a large percentage of each cycle). As aresult, the power used to generate an image with a given perceivedbrightness may be less as compared to conventional display technologieswith lower duty cycles. In some embodiments, the duty cycle may be 70%or more, 80% or more, or 90% or more. In some embodiments, the dutycycle may be about 99%. In addition, as noted herein, micro-displays mayfacilitate exceptionally high frame rates, which may provide advantagesincluding reducing mismatches between the position of a user's head andthe displayed content.

Reference will now be made to the drawings, in which like referencenumerals refer to like parts throughout. Unless indicated otherwise, thedrawings are schematic and not necessarily drawn to scale.

FIG. 2 illustrates a conventional display system for simulatingthree-dimensional imagery for a user. It will be appreciated that auser's eyes are spaced apart and that, when looking at a real object inspace, each eye will have a slightly different view of the object andmay form an image of the object at different locations on the retina ofeach eye. This may be referred to as binocular disparity and may beutilized by the human visual system to provide a perception of depth.Conventional display systems simulate binocular disparity by presentingtwo distinct images 190, 200 with slightly different views of the samevirtual object—one for each eye 210, 220—corresponding to the views ofthe virtual object that would be seen by each eye were the virtualobject a real object at a desired depth. These images provide binocularcues that the user's visual system may interpret to derive a perceptionof depth.

With continued reference to FIG. 2, the images 190, 200 are spaced fromthe eyes 210, 220 by a distance 230 on a z-axis. The z-axis is parallelto the optical axis of the viewer with their eyes fixated on an objectat optical infinity directly ahead of the viewer. The images 190, 200are flat and at a fixed distance from the eyes 210, 220. Based on theslightly different views of a virtual object in the images presented tothe eyes 210, 220, respectively, the eyes may naturally rotate such thatan image of the object falls on corresponding points on the retinas ofeach of the eyes, to maintain single binocular vision. This rotation maycause the lines of sight of each of the eyes 210, 220 to converge onto apoint in space at which the virtual object is perceived to be present.As a result, providing three-dimensional imagery conventionally involvesproviding binocular cues that may manipulate the vergence of the user'seyes 210, 220, and that the human visual system interprets to provide aperception of depth.

Generating a realistic and comfortable perception of depth ischallenging, however. It will be appreciated that light from objects atdifferent distances from the eyes have wavefronts with different amountsof divergence. FIGS. 3A-3C illustrate relationships between distance andthe divergence of light rays. The distance between the object and theeye 210 is represented by, in order of decreasing distance, R1, R2, andR3. As shown in FIGS. 3A-3C, the light rays become more divergent asdistance to the object decreases. Conversely, as distance increases, thelight rays become more collimated. Stated another way, it may be saidthat the light field produced by a point (the object or a part of theobject) has a spherical wavefront curvature, which is a function of howfar away the point is from the eye of the user. The curvature increaseswith decreasing distance between the object and the eye 210. While onlya single eye 210 is illustrated for clarity of illustration in FIGS.3A-3C and other figures herein, the discussions regarding eye 210 may beapplied to both eyes 210 and 220 of a viewer.

With continued reference to FIGS. 3A-3C, light from an object that theviewer's eyes are fixated on may have different degrees of wavefrontdivergence. Due to the different amounts of wavefront divergence, thelight may be focused differently by the lens of the eye, which in turnmay require the lens to assume different shapes to form a focused imageon the retina of the eye. Where a focused image is not formed on theretina, the resulting retinal blur acts as a cue to accommodation thatcauses a change in the shape of the lens of the eye until a focusedimage is formed on the retina. For example, the cue to accommodation maytrigger the ciliary muscles surrounding the lens of the eye to relax orcontract, thereby modulating the force applied to the suspensoryligaments holding the lens, thus causing the shape of the lens of theeye to change until retinal blur of an object of fixation is eliminatedor minimized, thereby forming a focused image of the object of fixationon the retina (e.g., fovea) of the eye. The process by which the lens ofthe eye changes shape may be referred to as accommodation, and the shapeof the lens of the eye required to form a focused image of the object offixation on the retina (e.g., fovea) of the eye may be referred to as anaccommodative state.

With reference now to FIG. 4A, a representation of theaccommodation-vergence response of the human visual system isillustrated. The movement of the eyes to fixate on an object causes theeyes to receive light from the object, with the light forming an imageon each of the retinas of the eyes. The presence of retinal blur in theimage formed on the retina may provide a cue to accommodation, and therelative locations of the image on the retinas may provide a cue tovergence. The cue to accommodation causes accommodation to occur,resulting in the lenses of the eyes each assuming a particularaccommodative state that forms a focused image of the object on theretina (e.g., fovea) of the eye. On the other hand, the cue to vergencecauses vergence movements (rotation of the eyes) to occur such that theimages formed on each retina of each eye are at corresponding retinalpoints that maintain single binocular vision. In these positions, theeyes may be said to have assumed a particular vergence state. Withcontinued reference to FIG. 4A, accommodation may be understood to bethe process by which the eye achieves a particular accommodative state,and vergence may be understood to be the process by which the eyeachieves a particular vergence state. As indicated in FIG. 4A, theaccommodative and vergence states of the eyes may change if the userfixates on another object. For example, the accommodated state maychange if the user fixates on a new object at a different depth on thez-axis.

Without being limited by theory, it is believed that viewers of anobject may perceive the object as being “three-dimensional” due to acombination of vergence and accommodation. As noted above, vergencemovements (e.g., rotation of the eyes so that the pupils move toward oraway from each other to converge the lines of sight of the eyes tofixate upon an object) of the two eyes relative to each other areclosely associated with accommodation of the lenses of the eyes. Undernormal conditions, changing the shapes of the lenses of the eyes tochange focus from one object to another object at a different distancewill automatically cause a matching change in vergence to the samedistance, under a relationship known as the “accommodation-vergencereflex.” Likewise, a change in vergence will trigger a matching changein lens shape under normal conditions.

With reference now to FIG. 4B, examples of different accommodative andvergence states of the eyes are illustrated. The pair of eyes 222 a isfixated on an object at optical infinity, while the pair eyes 222 b arefixated on an object 221 at less than optical infinity. Notably, thevergence states of each pair of eyes is different, with the pair of eyes222 a directed straight ahead, while the pair of eyes 222 converge onthe object 221. The accommodative states of the eyes forming each pairof eyes 222 a and 222 b are also different, as represented by thedifferent shapes of the lenses 210 a, 220 a.

Undesirably, many users of conventional “3-D” display systems find suchconventional systems to be uncomfortable or may not perceive a sense ofdepth at all due to a mismatch between accommodative and vergence statesin these displays. As noted above, many stereoscopic or “3-D” displaysystems display a scene by providing slightly different images to eacheye. Such systems are uncomfortable for many viewers, since they, amongother things, simply provide different presentations of a scene andcause changes in the vergence states of the eyes, but without acorresponding change in the accommodative states of those eyes. Rather,the images are shown by a display at a fixed distance from the eyes,such that the eyes view all the image information at a singleaccommodative state. Such an arrangement works against the“accommodation-vergence reflex” by causing changes in the vergence statewithout a matching change in the accommodative state. This mismatch isbelieved to cause viewer discomfort. Display systems that provide abetter match between accommodation and vergence may form more realisticand comfortable simulations of three-dimensional imagery.

Without being limited by theory, it is believed that the human eyetypically may interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited numbers of depthplanes. In some embodiments, the different presentations may provideboth cues to vergence and matching cues to accommodation, therebyproviding physiologically correct accommodation-vergence matching.

With continued reference to FIG. 4B, two depth planes 240, correspondingto different distances in space from the eyes 210, 220, are illustrated.For a given depth plane 240, vergence cues may be provided by thedisplaying of images of appropriately different perspectives for eacheye 210, 220. In addition, for a given depth plane 240, light formingthe images provided to each eye 210, 220 may have a wavefront divergencecorresponding to a light field produced by a point at the distance ofthat depth plane 240.

In the illustrated embodiment, the distance, along the z-axis, of thedepth plane 240 containing the point 221 is 1 m. As used herein,distances or depths along the z-axis may be measured with a zero-pointlocated at the exit pupils of the user's eyes. Thus, a depth plane 240located at a depth of 1 m corresponds to a distance of 1 m away from theexit pupils of the user's eyes, on the optical axis of those eyes withthe eyes directed towards optical infinity. As an approximation, thedepth or distance along the z-axis may be measured from the display infront of the user's eyes (e.g., from the surface of a waveguide), plus avalue for the distance between the device and the exit pupils of theuser's eyes. That value may be called the eye relief and corresponds tothe distance between the exit pupil of the user's eye and the displayworn by the user in front of the eye. In practice, the value for the eyerelief may be a normalized value used generally for all viewers. Forexample, the eye relief may be assumed to be 20 mm and a depth planethat is at a depth of 1 m may be at a distance of 980 mm in front of thedisplay.

With reference now to FIGS. 4C and 4D, examples of matchedaccommodation-vergence distances and mismatched accommodation-vergencedistances are illustrated, respectively. As illustrated in FIG. 4C, thedisplay system may provide images of a virtual object to each eye 210,220. The images may cause the eyes 210, 220 to assume a vergence statein which the eyes converge on a point 15 on a depth plane 240. Inaddition, the images may be formed by a light having a wavefrontcurvature corresponding to real objects at that depth plane 240. As aresult, the eyes 210, 220 assume an accommodative state in which theimages are in focus on the retinas of those eyes. Thus, the user mayperceive the virtual object as being at the point 15 on the depth plane240.

It will be appreciated that each of the accommodative and vergencestates of the eyes 210, 220 are associated with a particular distance onthe z-axis. For example, an object at a particular distance from theeyes 210, 220 causes those eyes to assume particular accommodativestates based upon the distances of the object. The distance associatedwith a particular accommodative state may be referred to as theaccommodation distance, Ad. Similarly, there are particular vergencedistances, Vd, associated with the eyes in particular vergence states,or positions relative to one another. Where the accommodation distanceand the vergence distance match, the relationship between accommodationand vergence may be said to be physiologically correct. This isconsidered to be the most comfortable scenario for a viewer.

In stereoscopic displays, however, the accommodation distance and thevergence distance may not always match. For example, as illustrated inFIG. 4D, images displayed to the eyes 210, 220 may be displayed withwavefront divergence corresponding to depth plane 240, and the eyes 210,220 may assume a particular accommodative state in which the points 15a, 15 b on that depth plane are in focus. However, the images displayedto the eyes 210, 220 may provide cues for vergence that cause the eyes210, 220 to converge on a point 15 that is not located on the depthplane 240. As a result, the accommodation distance corresponds to thedistance from the exit pupils of the eyes 210, 220 to the depth plane240, while the vergence distance corresponds to the larger distance fromthe exit pupils of the eyes 210, 220 to the point 15, in someembodiments. The accommodation distance is different from the vergencedistance. Consequently, there is an accommodation-vergence mismatch.Such a mismatch is considered undesirable and may cause discomfort inthe user. It will be appreciated that the mismatch corresponds todistance (e.g., Vd-Ad) and may be characterized using diopters.

In some embodiments, it will be appreciated that a reference point otherthan exit pupils of the eyes 210, 220 may be utilized for determiningdistance for determining accommodation-vergence mismatch, so long as thesame reference point is utilized for the accommodation distance and thevergence distance. For example, the distances could be measured from thecornea to the depth plane, from the retina to the depth plane, from theeyepiece (e.g., a waveguide of the display device) to the depth plane,and so on.

Without being limited by theory, it is believed that users may stillperceive accommodation-vergence mismatches of up to about 0.25 diopter,up to about 0.33 diopter, and up to about 0.5 diopter as beingphysiologically correct, without the mismatch itself causing significantdiscomfort. In some embodiments, display systems disclosed herein (e.g.,the display system 250, FIG. 6) present images to the viewer havingaccommodation-vergence mismatch of about 0.5 diopter or less. In someother embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.33 diopter or less. In yetother embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.25 diopter or less, includingabout 0.1 diopter or less.

FIG. 5 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence. The displaysystem includes a waveguide 270 that is configured to receive light 770that is encoded with image information, and to output that light to theuser's eye 210. The waveguide 270 may output the light 650 with adefined amount of wavefront divergence corresponding to the wavefrontdivergence of a light field produced by a point on a desired depth plane240. In some embodiments, the same amount of wavefront divergence isprovided for all objects presented on that depth plane. In addition, itwill be illustrated that the other eye of the user may be provided withimage information from a similar waveguide.

In some embodiments, a single waveguide may be configured to outputlight with a set amount of wavefront divergence corresponding to asingle or limited number of depth planes and/or the waveguide may beconfigured to output light of a limited range of wavelengths.Consequently, in some embodiments, a plurality or stack of waveguidesmay be utilized to provide different amounts of wavefront divergence fordifferent depth planes and/or to output light of different ranges ofwavelengths. As used herein, it will be appreciated at a depth plane maybe planar or may follow the contours of a curved surface.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 250 includes a stack ofwaveguides, or stacked waveguide assembly, 260 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 270, 280, 290, 300, 310. It will be appreciated that thedisplay system 250 may be considered a light field display in someembodiments. In addition, the waveguide assembly 260 may also bereferred to as an eyepiece.

In some embodiments, the display system 250 may be configured to providesubstantially continuous cues to vergence and multiple discrete cues toaccommodation. The cues to vergence may be provided by displayingdifferent images to each of the eyes of the user, and the cues toaccommodation may be provided by outputting the light that forms theimages with selectable discrete amounts of wavefront divergence. Statedanother way, the display system 250 may be configured to output lightwith variable levels of wavefront divergence. In some embodiments, eachdiscrete level of wavefront divergence corresponds to a particular depthplane and may be provided by a particular one of the waveguides 270,280, 290, 300, 310.

With continued reference to FIG. 6, the waveguide assembly 260 may alsoinclude a plurality of features 320, 330, 340, 350 between thewaveguides. In some embodiments, the features 320, 330, 340, 350 may beone or more lenses. The waveguides 270, 280, 290, 300, 310 and/or theplurality of lenses 320, 330, 340, 350 may be configured to send imageinformation to the eye with various levels of wavefront curvature orlight ray divergence. Each waveguide level may be associated with aparticular depth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 360, 370,380, 390, 400 may function as a source of light for the waveguides andmay be utilized to inject image information into the waveguides 270,280, 290, 300, 310, each of which may be configured, as describedherein, to distribute incoming light across each respective waveguide,for output toward the eye 210. Light exits an output surface 410, 420,430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 andis injected into a corresponding input surface 460, 470, 480, 490, 500of the waveguides 270, 280, 290, 300, 310. In some embodiments, each ofthe input surfaces 460, 470, 480, 490, 500 may be an edge of acorresponding waveguide, or may be part of a major surface of thecorresponding waveguide (that is, one of the waveguide surfaces directlyfacing the world 510 or the viewer's eye 210). In some embodiments, asingle beam of light (e.g. a collimated beam) may be injected into eachwaveguide to output an entire field of cloned collimated beams that aredirected toward the eye 210 at particular angles (and amounts ofdivergence) corresponding to the depth plane associated with aparticular waveguide. In some embodiments, a single one of the imageinjection devices 360, 370, 380, 390, 400 may be associated with andinject light into a plurality (e.g., three) of the waveguides 270, 280,290, 300, 310.

In some embodiments, the image injection devices 360, 370, 380, 390, 400are discrete displays that each produce image information for injectioninto a corresponding waveguide 270, 280, 290, 300, 310, respectively. Insome other embodiments, the image injection devices 360, 370, 380, 390,400 are the output ends of a single multiplexed display which may, e.g.,pipe image information via one or more optical conduits (such as fiberoptic cables) to each of the image injection devices 360, 370, 380, 390,400. It will be appreciated that the image information provided by theimage injection devices 360, 370, 380, 390, 400 may include light ofdifferent wavelengths, or colors (e.g., different component colors, asdiscussed herein).

In some embodiments, the light injected into the waveguides 270, 280,290, 300, 310 is provided by a light projection system 520, whichcomprises a light module 530, which may include a light emitter, such asa light emitting diode (LED). The light from the light module 530 may bedirected to and modified by a light modulator 540, e.g., a spatial lightmodulator, via a beam splitter 550. The light modulator 540 may beconfigured to change the perceived intensity of the light injected intothe waveguides 270, 280, 290, 300, 310 to encode the light with imageinformation. Examples of spatial light modulators include liquid crystaldisplays (LCD) including a liquid crystal on silicon (LCOS) displays. Itwill be appreciated that the image injection devices 360, 370, 380, 390,400 are illustrated schematically and, in some embodiments, these imageinjection devices may represent different light paths and locations in acommon projection system configured to output light into associated onesof the waveguides 270, 280, 290, 300, 310. In some embodiments, thewaveguides of the waveguide assembly 260 may function as ideal lenswhile relaying light injected into the waveguides out to the user'seyes. In this conception, the object may be the spatial light modulator540 and the image may be the image on the depth plane.

In some embodiments, the display system 250 may be a scanning fiberdisplay comprising one or more scanning fibers configured to projectlight in various patterns (e.g., raster scan, spiral scan, Lissajouspatterns, etc.) into one or more waveguides 270, 280, 290, 300, 310 andultimately to the eye 210 of the viewer. In some embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a single scanning fiber or a bundle of scanningfibers configured to inject light into one or a plurality of thewaveguides 270, 280, 290, 300, 310. In some other embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a plurality of scanning fibers or a plurality ofbundles of scanning fibers, each of which are configured to inject lightinto an associated one of the waveguides 270, 280, 290, 300, 310. Itwill be appreciated that one or more optical fibers may be configured totransmit light from the light module 530 to the one or more waveguides270, 280, 290, 300, 310. It will be appreciated that one or moreintervening optical structures may be provided between the scanningfiber, or fibers, and the one or more waveguides 270, 280, 290, 300, 310to, e.g., redirect light exiting the scanning fiber into the one or morewaveguides 270, 280, 290, 300, 310.

A controller 560 controls the operation of one or more of the stackedwaveguide assembly 260, including operation of the image injectiondevices 360, 370, 380, 390, 400, the light source 530, and the lightmodulator 540. In some embodiments, the controller 560 is part of thelocal data processing module 140. The controller 560 includesprogramming (e.g., instructions in a non-transitory medium) thatregulates the timing and provision of image information to thewaveguides 270, 280, 290, 300, 310 according to, e.g., any of thevarious schemes disclosed herein. In some embodiments, the controllermay be a single integral device, or a distributed system connected bywired or wireless communication channels. The controller 560 may be partof the processing modules 140 or 150 (FIG. 9E) in some embodiments.

With continued reference to FIG. 6, the waveguides 270, 280, 290, 300,310 may be configured to propagate light within each respectivewaveguide by total internal reflection (TIR). The waveguides 270, 280,290, 300, 310 may each be planar or have another shape (e.g., curved),with major top and bottom surfaces and edges extending between thosemajor top and bottom surfaces. In the illustrated configuration, thewaveguides 270, 280, 290, 300, 310 may each include out-coupling opticalelements 570, 580, 590, 600, 610 that are configured to extract lightout of a waveguide by redirecting the light, propagating within eachrespective waveguide, out of the waveguide to output image informationto the eye 210. Extracted light may also be referred to as out-coupledlight and the out-coupling optical elements light may also be referredto light extracting optical elements. An extracted beam of light may beoutputted by the waveguide at locations at which the light propagatingin the waveguide strikes a light extracting optical element. Theout-coupling optical elements 570, 580, 590, 600, 610 may, for example,be gratings, including diffractive optical features, as discussedfurther herein. While illustrated disposed at the bottom major surfacesof the waveguides 270, 280, 290, 300, 310, for ease of description anddrawing clarity, in some embodiments, the out-coupling optical elements570, 580, 590, 600, 610 may be disposed at the top and/or bottom majorsurfaces, and/or may be disposed directly in the volume of thewaveguides 270, 280, 290, 300, 310, as discussed further herein. In someembodiments, the out-coupling optical elements 570, 580, 590, 600, 610may be formed in a layer of material that is attached to a transparentsubstrate to form the waveguides 270, 280, 290, 300, 310. In some otherembodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithicpiece of material and the out-coupling optical elements 570, 580, 590,600, 610 may be formed on a surface and/or in the interior of that pieceof material.

With continued reference to FIG. 6, as discussed herein, each waveguide270, 280, 290, 300, 310 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide270 nearest the eye may be configured to deliver collimated light (whichwas injected into such waveguide 270), to the eye 210. The collimatedlight may be representative of the optical infinity focal plane. Thenext waveguide up 280 may be configured to send out collimated lightwhich passes through the first lens 350 (e.g., a negative lens) beforeit may reach the eye 210; such first lens 350 may be configured tocreate a slight convex wavefront curvature so that the eye/braininterprets light coming from that next waveguide up 280 as coming from afirst focal plane closer inward toward the eye 210 from opticalinfinity. Similarly, the third up waveguide 290 passes its output lightthrough both the first 350 and second 340 lenses before reaching the eye210; the combined optical power of the first 350 and second 340 lensesmay be configured to create another incremental amount of wavefrontcurvature so that the eye/brain interprets light coming from the thirdwaveguide 290 as coming from a second focal plane that is even closerinward toward the person from optical infinity than was light from thenext waveguide up 280.

The other waveguide layers 300, 310 and lenses 330, 320 are similarlyconfigured, with the highest waveguide 310 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 320, 330, 340, 350 whenviewing/interpreting light coming from the world 510 on the other sideof the stacked waveguide assembly 260, a compensating lens layer 620 maybe disposed at the top of the stack to compensate for the aggregatepower of the lens stack 320, 330, 340, 350 below. Such a configurationprovides as many perceived focal planes as there are availablewaveguide/lens pairings. Both the out-coupling optical elements of thewaveguides and the focusing aspects of the lenses may be static (i.e.,not dynamic or electro-active). In some alternative embodiments, eitheror both may be dynamic using electro-active features.

In some embodiments, two or more of the waveguides 270, 280, 290, 300,310 may have the same associated depth plane. For example, multiplewaveguides 270, 280, 290, 300, 310 may be configured to output imagesset to the same depth plane, or multiple subsets of the waveguides 270,280, 290, 300, 310 may be configured to output images set to the sameplurality of depth planes, with one set for each depth plane. This mayprovide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 6, the out-coupling optical elements570, 580, 590, 600, 610 may be configured to both redirect light out oftheir respective waveguides and to output this light with theappropriate amount of divergence or collimation for a particular depthplane associated with the waveguide. As a result, waveguides havingdifferent associated depth planes may have different configurations ofout-coupling optical elements 570, 580, 590, 600, 610, which outputlight with a different amount of divergence depending on the associateddepth plane. In some embodiments, the light extracting optical elements570, 580, 590, 600, 610 may be volumetric or surface features, which maybe configured to output light at specific angles. For example, the lightextracting optical elements 570, 580, 590, 600, 610 may be volumeholograms, surface holograms, and/or diffraction gratings. In someembodiments, the features 320, 330, 340, 350 may not be lenses; rather,they may simply be spacers (e.g., cladding layers and/or structures forforming air gaps).

In some embodiments, the out-coupling optical elements 570, 580, 590,600, 610 are diffractive features that form a diffraction pattern, or“diffractive optical element” (also referred to herein as a “DOE”).Preferably, the DOE's have a sufficiently low diffraction efficiency sothat only a portion of the light of the beam is deflected away towardthe eye 210 with each intersection of the DOE, while the rest continuesto move through a waveguide via TIR. The light carrying the imageinformation is thus divided into a number of related exit beams thatexit the waveguide at a multiplicity of locations and the result is afairly uniform pattern of exit emission toward the eye 210 for thisparticular collimated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE maycomprise a layer of polymer dispersed liquid crystal, in whichmicrodroplets comprise a diffraction pattern in a host medium, and therefractive index of the microdroplets may be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet may be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

In some embodiments, a camera assembly 630 (e.g., a digital camera,including visible light and infrared light cameras) may be provided tocapture images of the eye 210 and/or tissue around the eye 210 to, e.g.,detect user inputs and/or to monitor the physiological state of theuser. As used herein, a camera may be any image capture device. In someembodiments, the camera assembly 630 may include an image capture deviceand a light source to project light (e.g., infrared light) to the eye,which may then be reflected by the eye and detected by the image capturedevice. In some embodiments, the camera assembly 630 may be attached tothe frame 80 (FIG. 9E) and may be in electrical communication with theprocessing modules 140 and/or 150, which may process image informationfrom the camera assembly 630. In some embodiments, one camera assembly630 may be utilized for each eye, to separately monitor each eye.

With reference now to FIG. 7, an example of exit beams outputted by awaveguide is shown. One waveguide is illustrated, but it will beappreciated that other waveguides in the waveguide assembly 260 (FIG. 6)may function similarly, where the waveguide assembly 260 includesmultiple waveguides. Light 640 is injected into the waveguide 270 at theinput surface 460 of the waveguide 270 and propagates within thewaveguide 270 by TIR. At points where the light 640 impinges on the DOE570, a portion of the light exits the waveguide as exit beams 650. Theexit beams 650 are illustrated as substantially parallel but, asdiscussed herein, they may also be redirected to propagate to the eye210 at an angle (e.g., forming divergent exit beams), depending on thedepth plane associated with the waveguide 270. It will be appreciatedthat substantially parallel exit beams may be indicative of a waveguidewith out-coupling optical elements that out-couple light to form imagesthat appear to be set on a depth plane at a large distance (e.g.,optical infinity) from the eye 210. Other waveguides or other sets ofout-coupling optical elements may output an exit beam pattern that ismore divergent, which would require the eye 210 to accommodate to acloser distance to bring it into focus on the retina and would beinterpreted by the brain as light from a distance closer to the eye 210than optical infinity.

In some embodiments, a full color image may be formed at each depthplane by overlaying images in each of the component colors, e.g., threeor more component colors. FIG. 8 illustrates an example of a stackedwaveguide assembly in which each depth plane includes images formedusing multiple different component colors. The illustrated embodimentshows depth planes 240 a—240 f, although more or fewer depths are alsocontemplated. Each depth plane may have three or more component colorimages associated with it, including: a first image of a first color, G;a second image of a second color, R; and a third image of a third color,B. Different depth planes are indicated in the figure by differentnumbers for diopters (dpt) following the letters G, R, and B. Just asexamples, the numbers following each of these letters indicate diopters(1/m), or inverse distance of the depth plane from a viewer, and eachbox in the figures represents an individual component color image. Insome embodiments, to account for differences in the eye's focusing oflight of different wavelengths, the exact placement of the depth planesfor different component colors may vary. For example, differentcomponent color images for a given depth plane may be placed on depthplanes corresponding to different distances from the user. Such anarrangement may increase visual acuity and user comfort and/or maydecrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by asingle dedicated waveguide and, consequently, each depth plane may havemultiple waveguides associated with it. In such embodiments, each box inthe figures including the letters G, R, or B may be understood torepresent an individual waveguide, and three waveguides may be providedper depth plane where three component color images are provided perdepth plane. While the waveguides associated with each depth plane areshown adjacent to one another in this drawing for ease of description,it will be appreciated that, in a physical device, the waveguides mayall be arranged in a stack with one waveguide per level. In some otherembodiments, multiple component colors may be outputted by the samewaveguide, such that, e.g., only a single waveguide may be provided perdepth plane.

With continued reference to FIG. 8, in some embodiments, G is the colorgreen, R is the color red, and B is the color blue. In some otherembodiments, other colors associated with other wavelengths of light,including magenta and cyan, may be used in addition to or may replaceone or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

In some embodiments, the light source 530 (FIG. 6) may be configured toemit light of one or more wavelengths outside the visual perceptionrange of the viewer, for example, infrared and/or ultravioletwavelengths. In addition, the in-coupling, out-coupling, and other lightredirecting structures of the waveguides of the display 250 may beconfigured to direct and emit this light out of the display towards theuser's eye 210, e.g., for imaging and/or user stimulation applications.

With reference now to FIG. 9A, in some embodiments, light impinging on awaveguide may need to be redirected to in-couple that light into thewaveguide. An in-coupling optical element may be used to redirect andin-couple the light into its corresponding waveguide. FIG. 9Aillustrates a cross-sectional side view of an example of a plurality orset 660 of stacked waveguides that each includes an in-coupling opticalelement. The waveguides may each be configured to output light of one ormore different wavelengths, or one or more different ranges ofwavelengths. It will be appreciated that the stack 660 may correspond tothe stack 260 (FIG. 6) and the illustrated waveguides of the stack 660may correspond to part of the plurality of waveguides 270, 280, 290,300, 310, except that light from one or more of the image injectiondevices 360, 370, 380, 390, 400 is injected into the waveguides from aposition that requires light to be redirected for in-coupling.

The illustrated set 660 of stacked waveguides includes waveguides 670,680, and 690. Each waveguide includes an associated in-coupling opticalelement (which may also be referred to as a light input area on thewaveguide), with, e.g., in-coupling optical element 700 disposed on amajor surface (e.g., an upper major surface) of waveguide 670,in-coupling optical element 710 disposed on a major surface (e.g., anupper major surface) of waveguide 680, and in-coupling optical element720 disposed on a major surface (e.g., an upper major surface) ofwaveguide 690. In some embodiments, one or more of the in-couplingoptical elements 700, 710, 720 may be disposed on the bottom majorsurface of the respective waveguide 670, 680, 690 (particularly wherethe one or more in-coupling optical elements are reflective, deflectingoptical elements). As illustrated, the in-coupling optical elements 700,710, 720 may be disposed on the upper major surface of their respectivewaveguide 670, 680, 690 (or the top of the next lower waveguide),particularly where those in-coupling optical elements are transmissive,deflecting optical elements. In some embodiments, the in-couplingoptical elements 700, 710, 720 may be disposed in the body of therespective waveguide 670, 680, 690. In some embodiments, as discussedherein, the in-coupling optical elements 700, 710, 720 are wavelengthselective, such that they selectively redirect one or more wavelengthsof light, while transmitting other wavelengths of light. Whileillustrated on one side or corner of their respective waveguide 670,680, 690, it will be appreciated that the in-coupling optical elements700, 710, 720 may be disposed in other areas of their respectivewaveguide 670, 680, 690 in some embodiments.

As illustrated, the in-coupling optical elements 700, 710, 720 may belaterally offset from one another, as seen in the illustrated head-onview in a direction of light propagating to these in-coupling opticalelements. In some embodiments, each in-coupling optical element may beoffset such that it receives light without that light passing throughanother in-coupling optical element. For example, each in-couplingoptical element 700, 710, 720 may be configured to receive light from adifferent image injection device 360, 370, 380, 390, and 400 as shown inFIG. 6, and may be separated (e.g., laterally spaced apart) from otherin-coupling optical elements 700, 710, 720 such that it substantiallydoes not receive light from the other ones of the in-coupling opticalelements 700, 710, 720.

Each waveguide also includes associated light distributing elements,with, e.g., light distributing elements 730 disposed on a major surface(e.g., a top major surface) of waveguide 670, light distributingelements 740 disposed on a major surface (e.g., a top major surface) ofwaveguide 680, and light distributing elements 750 disposed on a majorsurface (e.g., a top major surface) of waveguide 690. In some otherembodiments, the light distributing elements 730, 740, 750, may bedisposed on a bottom major surface of associated waveguides 670, 680,690, respectively. In some other embodiments, the light distributingelements 730, 740, 750, may be disposed on both top and bottom majorsurface of associated waveguides 670, 680, 690, respectively; or thelight distributing elements 730, 740, 750, may be disposed on differentones of the top and bottom major surfaces in different associatedwaveguides 670, 680, 690, respectively.

The waveguides 670, 680, 690 may be spaced apart and separated by, e.g.,gas, liquid, and/or solid layers of material. For example, asillustrated, layer 760 a may separate waveguides 670 and 680; and layer760 b may separate waveguides 680 and 690. In some embodiments, thelayers 760 a and 760 b are formed of low refractive index materials(that is, materials having a lower refractive index than the materialforming the immediately adjacent one of waveguides 670, 680, 690).Preferably, the refractive index of the material forming the layers 760a, 760 b is 0.05 or more, or 0.10 or less than the refractive index ofthe material forming the waveguides 670, 680, 690. Advantageously, thelower refractive index layers 760 a, 760 b may function as claddinglayers that facilitate total internal reflection (TIR) of light throughthe waveguides 670, 680, 690 (e.g., TIR between the top and bottom majorsurfaces of each waveguide). In some embodiments, the layers 760 a, 760b are formed of air. While not illustrated, it will be appreciated thatthe top and bottom of the illustrated set 660 of waveguides may includeimmediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the waveguides 670, 680, 690 are similar or the same,and the material forming the layers 760 a, 760 b are similar or thesame. In some embodiments, the material forming the waveguides 670, 680,690 may be different between one or more waveguides, and/or the materialforming the layers 760 a, 760 b may be different, while still holding tothe various refractive index relationships noted above.

With continued reference to FIG. 9A, light rays 770, 780, 790 areincident on the set 660 of waveguides. It will be appreciated that thelight rays 770, 780, 790 may be injected into the waveguides 670, 680,690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG.6).

In some embodiments, the light rays 770, 780, 790 have differentproperties, e.g., different wavelengths or different ranges ofwavelengths, which may correspond to different colors. The in-couplingoptical elements 700, 710, 720 each deflect the incident light such thatthe light propagates through a respective one of the waveguides 670,680, 690 by TIR. In some embodiments, the in-coupling optical elements700, 710, 720 each selectively deflect one or more particularwavelengths of light, while transmitting other wavelengths to anunderlying waveguide and associated in-coupling optical element.

For example, in-coupling optical element 700 may be configured todeflect ray 770, which has a first wavelength or range of wavelengths,while transmitting rays 780 and 790, which have different second andthird wavelengths or ranges of wavelengths, respectively. Thetransmitted ray 780 impinges on and is deflected by the in-couplingoptical element 710, which is configured to deflect light of a secondwavelength or range of wavelengths. The ray 790 is deflected by thein-coupling optical element 720, which is configured to selectivelydeflect light of third wavelength or range of wavelengths.

With continued reference to FIG. 9A, the deflected light rays 770, 780,790 are deflected so that they propagate through a correspondingwaveguide 670, 680, 690; that is, the in-coupling optical elements 700,710, 720 of each waveguide deflects light into that correspondingwaveguide 670, 680, 690 to in-couple light into that correspondingwaveguide. The light rays 770, 780, 790 are deflected at angles thatcause the light to propagate through the respective waveguide 670, 680,690 by TIR. The light rays 770, 780, 790 propagate through therespective waveguide 670, 680, 690 by TIR until impinging on thewaveguide's corresponding light distributing elements 730, 740, 750.

With reference now to FIG. 9B, a perspective view of an example of theplurality of stacked waveguides of FIG. 9A is illustrated. As notedabove, the in-coupled light rays 770, 780, 790, are deflected by thein-coupling optical elements 700, 710, 720, respectively, and thenpropagate by TIR within the waveguides 670, 680, 690, respectively. Thelight rays 770, 780, 790 then impinge on the light distributing elements730, 740, 750, respectively. The light distributing elements 730, 740,750 deflect the light rays 770, 780, 790 so that they propagate towardsthe out-coupling optical elements 800, 810, 820, respectively.

In some embodiments, the light distributing elements 730, 740, 750 areorthogonal pupil expanders (OPE's). In some embodiments, the OPE'sdeflect or distribute light to the out-coupling optical elements 800,810, 820 and, in some embodiments, may also increase the beam or spotsize of this light as it propagates to the out-coupling opticalelements. In some embodiments, the light distributing elements 730, 740,750 may be omitted and the in-coupling optical elements 700, 710, 720may be configured to deflect light directly to the out-coupling opticalelements 800, 810, 820. For example, with reference to FIG. 9A, thelight distributing elements 730, 740, 750 may be replaced without-coupling optical elements 800, 810, 820, respectively. In someembodiments, the out-coupling optical elements 800, 810, 820 are exitpupils (EP's) or exit pupil expanders (EPE's) that direct light in aviewer's eye 210 (FIG. 7). It will be appreciated that the OPE's may beconfigured to increase the dimensions of the eye box in at least oneaxis and the EPE's may be to increase the eye box in an axis crossing,e.g., orthogonal to, the axis of the OPEs. For example, each OPE may beconfigured to redirect a portion of the light striking the OPE to an EPEof the same waveguide, while allowing the remaining portion of the lightto continue to propagate down the waveguide. Upon impinging on the OPEagain, another portion of the remaining light is redirected to the EPE,and the remaining portion of that portion continues to propagate furtherdown the waveguide, and so on. Similarly, upon striking the EPE, aportion of the impinging light is directed out of the waveguide towardsthe user, and a remaining portion of that light continues to propagatethrough the waveguide until it strikes the EP again, at which timeanother portion of the impinging light is directed out of the waveguide,and so on. Consequently, a single beam of in-coupled light may be“replicated” each time a portion of that light is redirected by an OPEor EPE, thereby forming a field of cloned beams of light, as shown inFIG. 6. In some embodiments, the OPE and/or EPE may be configured tomodify a size of the beams of light.

Accordingly, with reference to FIGS. 9A and 9B, in some embodiments, theset 660 of waveguides includes waveguides 670, 680, 690; in-couplingoptical elements 700, 710, 720; light distributing elements (e.g.,OPE's) 730, 740, 750; and out-coupling optical elements (e.g., EP's)800, 810, 820 for each component color. The waveguides 670, 680, 690 maybe stacked with an air gap/cladding layer between each one. Thein-coupling optical elements 700, 710, 720 redirect or deflect incidentlight (with different in-coupling optical elements receiving light ofdifferent wavelengths) into its waveguide. The light then propagates atan angle which will result in TIR within the respective waveguide 670,680, 690. In the example shown, light ray 770 (e.g., blue light) isdeflected by the first in-coupling optical element 700, and thencontinues to bounce down the waveguide, interacting with the lightdistributing element (e.g., OPE's) 730 and then the out-coupling opticalelement (e.g., EPs) 800, in a manner described earlier. The light rays780 and 790 (e.g., green and red light, respectively) will pass throughthe waveguide 670, with light ray 780 impinging on and being deflectedby in-coupling optical element 710. The light ray 780 then bounces downthe waveguide 680 via TIR, proceeding on to its light distributingelement (e.g., OPEs) 740 and then the out-coupling optical element(e.g., EP's) 810. Finally, light ray 790 (e.g., red light) passesthrough the waveguide 690 to impinge on the light in-coupling opticalelements 720 of the waveguide 690. The light in-coupling opticalelements 720 deflect the light ray 790 such that the light raypropagates to light distributing element (e.g., OPEs) 750 by TIR, andthen to the out-coupling optical element (e.g., EPs) 820 by TIR. Theout-coupling optical element 820 then finally out-couples the light ray790 to the viewer, who also receives the out-coupled light from theother waveguides 670, 680.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B. It will be appreciated thatthis top-down view may also be referred to as a head-on view, as seen inthe direction of propagation of light towards the in-coupling opticalelements 800, 810, 820; that is, the top-down view is a view of thewaveguides with image light incident normal to the page. As illustrated,the waveguides 670, 680, 690, along with each waveguide's associatedlight distributing element 730, 740, 750 and associated out-couplingoptical element 800, 810, 820, may be vertically aligned. However, asdiscussed herein, the in-coupling optical elements 700, 710, 720 are notvertically aligned; rather, the in-coupling optical elements arepreferably non-overlapping (e.g., laterally spaced apart as seen in thetop-down view). As discussed further herein, this nonoverlapping spatialarrangement facilitates the injection of light from different sourcesinto different waveguides on a one-to-one basis, thereby allowing aspecific light source to be uniquely coupled to a specific waveguide. Insome embodiments, arrangements including nonoverlappingspatially-separated in-coupling optical elements may be referred to as ashifted pupil system, and the in-coupling optical elements within thesearrangements may correspond to sub-pupils.

It will be appreciated that the spatially overlapping areas may havelateral overlap of 70% or more, 80% or more, or 90% or more of theirareas, as seen in the top-down view. On the other hand, the laterallyshifted areas of less than 30% overlap, less than 20% overlap, or lessthan 10% overlap of their areas, as seen in top-down view. In someembodiments, laterally shifted areas have no overlap.

FIG. 9D illustrates a top-down plan view of another example of aplurality of stacked waveguides. As illustrated, the waveguides 670,680, 690 may be vertically aligned. However, in comparison to theconfiguration of FIG. 9C, separate light distributing elements 730, 740,750 and associated out-coupling optical elements 800, 810, 820 areomitted. Instead, light distributing elements and out-coupling opticalelements are effectively superimposed and occupy the same area as seenin the top-down view. In some embodiments, light distributing elements(e.g., OPE's) may be disposed on one major surface of the waveguides670, 680, 690 and out-coupling optical elements (e.g., EPE's) may bedisposed on the other major surface of those waveguides. Thus, eachwaveguide 670, 680, 690 may have superimposed light distributing and outcoupling optical elements, collectively referred to as combinedOPE/EPE's 1281, 1282, 1283, respectively. Further details regarding suchcombined OPE/EPE's may be found in U.S. application Ser. No. 16/221,359,filed on Dec. 14, 2018, the entire disclosure of which is incorporatedby reference herein. The in-coupling optical elements 700, 710, 720in-couple and direct light to the combined OPE/EPE's 1281, 1282, 1283,respectively. In some embodiments, as illustrated, the in-couplingoptical elements 700, 710, 720 may be laterally shifted (e.g., they arelaterally spaced apart as seen in the illustrated top-down view) in havea shifted pupil spatial arrangement. As with the configuration of FIG.9C, this laterally-shifted spatial arrangement facilitates the injectionof light of different wavelengths (e.g., from different light sources)into different waveguides on a one-to-one basis.

FIG. 9E illustrates an example of wearable display system 60 into whichthe various waveguides and related systems disclosed herein may beintegrated. In some embodiments, the display system 60 is the system 250of FIG. 6, with FIG. 6 schematically showing some parts of that system60 in greater detail. For example, the waveguide assembly 260 of FIG. 6may be part of the display 70.

With continued reference to FIG. 9E, the display system 60 includes adisplay 70, and various mechanical and electronic modules and systems tosupport the functioning of that display 70. The display 70 may becoupled to a frame 80, which is wearable by a display system user orviewer 90 and which is configured to position the display 70 in front ofthe eyes of the user 90. The display 70 may be considered eyewear insome embodiments. The display 70 may include one or more waveguides,such as the waveguide 270, configured to relay in-coupled image lightand to output that image light to an eye of the user 90. In someembodiments, a speaker 100 is coupled to the frame 80 and configured tobe positioned adjacent the ear canal of the user 90 (in someembodiments, another speaker, not shown, may optionally be positionedadjacent the other ear canal of the user to provide stereo/shapeablesound control). The display system 60 may also include one or moremicrophones 110 or other devices to detect sound. In some embodiments,the microphone is configured to allow the user to provide inputs orcommands to the system 60 (e.g., the selection of voice menu commands,natural language questions, etc.), and/or may allow audio communicationwith other persons (e.g., with other users of similar display systems.The microphone may further be configured as a peripheral sensor tocollect audio data (e.g., sounds from the user and/or environment). Insome embodiments, the display system 60 may further include one or moreoutwardly-directed environmental sensors 112 configured to detectobjects, stimuli, people, animals, locations, or other aspects of theworld around the user. For example, environmental sensors 112 mayinclude one or more cameras, which may be located, for example, facingoutward so as to capture images similar to at least a portion of anordinary field of view of the user 90. In some embodiments, the displaysystem may also include a peripheral sensor 120 a, which may be separatefrom the frame 80 and attached to the body of the user 90 (e.g., on thehead, torso, an extremity, etc. of the user 90). The peripheral sensor120 a may be configured to acquire data characterizing a physiologicalstate of the user 90 in some embodiments. For example, the sensor 120 amay be an electrode.

With continued reference to FIG. 9E, the display 70 is operativelycoupled by communications link 130, such as by a wired lead or wirelessconnectivity, to a local data processing module 140 which may be mountedin a variety of configurations, such as fixedly attached to the frame80, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 90 (e.g., in abackpack-style configuration, in a belt-coupling style configuration).Similarly, the sensor 120 a may be operatively coupled by communicationslink 120 b, e.g., a wired lead or wireless connectivity, to the localprocessor and data module 140. The local processing and data module 140may comprise a hardware processor, as well as digital memory, such asnon-volatile memory (e.g., flash memory or hard disk drives), both ofwhich may be utilized to assist in the processing, caching, and storageof data. Optionally, the local processor and data module 140 may includeone or more central processing units (CPUs), graphics processing units(GPUs), dedicated processing hardware, and so on. The data may includedata a) captured from sensors (which may be, e.g., operatively coupledto the frame 80 or otherwise attached to the user 90), such as imagecapture devices (such as cameras), microphones, inertial measurementunits, accelerometers, compasses, GPS units, radio devices, gyros,and/or other sensors disclosed herein; and/or b) acquired and/orprocessed using remote processing module 150 and/or remote datarepository 160 (including data relating to virtual content), possiblyfor passage to the display 70 after such processing or retrieval. Thelocal processing and data module 140 may be operatively coupled bycommunication links 170, 180, such as via a wired or wirelesscommunication links, to the remote processing module 150 and remote datarepository 160 such that these remote modules 150, 160 are operativelycoupled to each other and available as resources to the local processingand data module 140. In some embodiments, the local processing and datamodule 140 may include one or more of the image capture devices,microphones, inertial measurement units, accelerometers, compasses, GPSunits, radio devices, and/or gyros. In some other embodiments, one ormore of these sensors may be attached to the frame 80, or may bestandalone structures that communicate with the local processing anddata module 140 by wired or wireless communication pathways.

With continued reference to FIG. 9E, in some embodiments, the remoteprocessing module 150 may comprise one or more processors configured toanalyze and process data and/or image information, for instanceincluding one or more central processing units (CPUs), graphicsprocessing units (GPUs), dedicated processing hardware, and so on. Insome embodiments, the remote data repository 160 may comprise a digitaldata storage facility, which may be available through the internet orother networking configuration in a “cloud” resource configuration. Insome embodiments, the remote data repository 160 may include one or moreremote servers, which provide information, e.g., information forgenerating virtual content, to the local processing and data module 140and/or the remote processing module 150. In some embodiments, all datais stored and all computations are performed in the local processing anddata module, allowing fully autonomous use from a remote module.Optionally, an outside system (e.g., a system of one or more processors,one or more computers) that includes CPUs, GPUs, and so on, may performat least a portion of processing (e.g., generating image information,processing data) and provide information to, and receive informationfrom, modules 140, 150, 160, for instance via wireless or wiredconnections.

FIG. 10 illustrates an example of a wearable display system with a lightprojection system 910 having a spatial light modulator 930 and aseparate light source 940. The light source 940 may comprise one or morelight emitters and illuminates the spatial light modulator (SLM) 930. Alens structure 960 may be used to focus the light from the light source940 onto the SLM 930. A beam splitter (e.g., a polarizing beam splitter(PBS)) 950 reflects light from the light source 940 to the spatial lightmodulator 930, which reflects and modulates the light. The reflectedmodulated light, also referred to as image light, then propagatesthrough the beam splitter 950 to the eyepiece 920. Another lensstructure, projection optics 970, may be utilized to converge or focusthe image light onto the eyepiece 920. The eyepiece 920 may include oneor more waveguides or waveguides that relay the modulated to the eye210.

As noted herein, the separate light source 940 and associated lensstructure 960 may undesirably add weight and size to the wearabledisplay system. This may decrease the comfort of the display system,particularly for a user wearing the display system for an extendedduration.

In addition, the light source 940 in conjunction with the SLM 930 mayconsume energy inefficiently. For example, the light source 940 mayilluminate the entirety of the SLM 930. The SLM 930 then selectivelyreflects light towards the eyepiece 920. thus, not all the lightproduced by the light source 940 may be utilized to form an image; someof this light, e.g., light corresponding to dark regions of an image, isnot reflected to the eyepiece 920. As a result, the light source 940utilizes energy to generate light to illuminate the entirety of the SLM930, but only a fraction of this light may be needed to form someimages.

Moreover, as noted herein, in some cases, the SLM 930 may modulate lightusing a micro-mirror to selectively reflect incident light, or usingliquid crystal molecules that modify the amount of light reflected froman underlying mirror. As a result, such devices require physicalmovement of optical elements (e.g., micro-mirrors or liquid crystalmolecules) in order to modulate light from the light source 940. Thephysical movement required to modulate light to encode the light withimage information, e.g., corresponding to a pixel, may occur atrelatively slow speeds in comparison to, e.g., the ability to turn anLED or OLED “on” or “off”. This relatively slow movement may limit theframe rate of the display system and may be visible as, e.g., motionblur, color-breakup, and/or presented images that are mismatched withthe pose of the user's head or changes in said pose.

Advantageously, wearable displays utilizing emissive micro-displays, asdisclosed herein, may facilitate wearable display systems that have arelatively low weight and bulkiness, high energy efficiency, and highframe rate, with low motion blur and low motion-to-photon latency. Lowblur and low motion-to-photon latency are further discussed in U.S.Provisional Application No. 62/786,199, filed Dec. 28, 2018, the entiredisclosure of which is incorporated by reference herein. In addition, incomparison to scanning fiber displays, the emissive micro-displays mayavoid artifacts caused by the use of coherent light sources.

With reference now to FIG. 11A, an example is illustrated of a wearabledisplay system with a light projection system 1010 having multipleemissive micro-displays 1030 a, 1030 b, 1030 c. Light from themicro-displays 1030 a, 1030 b, 1030 c is combined by an optical combiner1050 and directed towards an eyepiece 1020, which relays the light tothe eye 210 of a user. Projection optics 1070 may be provided betweenthe optical combiner 1050 and the eyepiece 1020. In some embodiments,the eyepiece 1020 may be a waveguide assembly comprising one or morewaveguides. In some embodiments, the light projection system 1010 andthe eyepiece 1020 may be supported (e.g., attached to) the frame 80(FIG. 9E).

In some embodiments, the micro-displays 1030 a, 1030 b, 1030 c may bemonochrome micro-displays, with each monochrome micro-display outputtinglight of a different component color to provide a monochrome image. Asdiscussed herein, the monochrome images combine to form a full-colorimage.

In some other embodiments, the micro-displays 1030 a, 1030 b, 1030 c maybe may each be full-color displays configured to output light of allcomponent colors. For example, the micro-displays 1030 a, 1030 b, 1030 ceach include red, green, and blue light emitters. The micro-displays1030 a, 1030 b, 1030 c may be identical and may display the same image.However, utilizing multiple micro-displays may provide advantages forincreasing the brightness and brightness dynamic range of the brightnessof the image, by combining the light from the multiple micro-displays toform a single image. In some embodiments, two or more (e.g., three)micro-displays may be utilized, with the optical combiner 1050 isconfigured to combine light from all of these micro-displays.

The micro-displays may comprise an array of light emitters. Examples oflight emitters include organic light-emitting diodes (OLEDs) andmicro-light-emitting diodes (micro-LEDs). It will be appreciated thatOLEDs utilize organic material to emit light and micro-LEDs utilizeinorganic material to emit light. Advantageously, some micro-LEDsprovide higher luminance and higher efficiency (in terms of lux/W) thanOLEDs. In some embodiments, the micro-displays are preferably micro-LEDdisplays.

With continued reference to FIG. 11A, the micro-displays 1030 a, 1030 b,1030 c may each be configured to emit image light 1032 a, 1032 b, 1032c. Where the micro-displays are monochrome micro-displays, the imagelight 1032 a, 1032 b, 1032 c may each be of a different component color.The optical combiner 1050 receives the image light 1032 a, 1032 b, 1032c and effectively combines this light such that the light propagatesgenerally in the same direction, e.g., toward the projection optics1070. In some embodiments, the optical combiner 1050 may be a dichroicX-cube prism having reflective internal surfaces that redirect the imagelight 1032 a, 1032 b, 1032 c to the projection optics 1070. It will beappreciated that the projection optics 1070 may be a lens structurecomprising one or more lenses which converge or focus image light ontothe eyepiece 1020. The eyepiece 1020 then relays the image light 1032 a,1032 b, 1032 c to the eye 210.

In some embodiments, the eyepiece 1020 may comprise a plurality ofstacked waveguides 1020 a, 1020 b, 1020 c, each of which has arespective in-coupling optical element 1022 a, 1022 b, 1022 c. In someembodiments, the number of waveguides is proportional to the number ofcomponent colors provided by the micro-displays 1030 a, 1030 b, 1030 c.For example, where there are three component colors, the number ofwaveguides in the eyepiece 1020 may include a set of three waveguides ormultiple sets of three waveguides each. In some embodiments, each setmay output light with wavefront divergence corresponding to a particulardepth plane, as discussed herein. It will be appreciated that thewaveguides 1020 a, 1020 b, 1020 c and the in-coupling optical element1022 a, 1022 b, 1022 c may correspond to the waveguides 670, 680, 690and the in-coupling optical elements 700, 710, 720, respectively, ofFIGS. 9A-9C. As viewed from the projection optics 1070, the in-couplingoptical elements 1022 a, 1022 b, 1022 c may be laterally shifted, suchthat they at least partly do not overlap as seen in such a view.

As illustrated, the various in-coupling optical elements disclosedherein (e.g., the in-coupling optical element 1022 a, 1022 b, 1022 c)may be disposed on a major surface of an associated waveguide (e.g.,waveguides 1020 a, 1020 b, 1020 c, respectively). In addition, as alsoillustrated, the major surface on which a given in-coupling opticalelement is disposed may be the rear surface of the waveguide. In such aconfiguration, the in-coupling optical element may be a reflective lightredirecting element, which in-couples light by reflecting the light atangles which support TIR through the associated waveguide. In some otherconfigurations, the in-coupling optical element may be disposed on theforward surface of the waveguide (closer to the projection optics 1070than the rearward surface). In such configurations, the in-couplingoptical element may be a transmissive light redirecting element, whichin-couples light by changing the direction of propagation of light asthe light is transmitted through the in-coupling optical element. Itwill be appreciated that any of the in-coupling optical elementsdisclosed herein may be reflective or transmissive in-coupling opticalelements.

With continued reference to FIG. 11A, image light 1032 a, 1032 b, 1032 cfrom different ones of the micro-displays 1030 a, 1030 b, 1030 c maytake different paths to the eyepiece 1020, such that they impinge ondifferent ones of the in-coupling optical element 1022 a, 1022 b, 1022c. Where the image light 1032 a, 1032 b, 1032 c includes light ofdifferent component colors, the associated in-coupling optical element1022 a, 1022 b, 1022 c, respectively, may be configured to selectivelyin couple light of different wavelengths, as discussed above regarding,e.g., the in-coupling optical elements 700, 710, 720 of FIGS. 9A-9C.

With continued reference to FIG. 11A, the optical combiner 1050 may beconfigured to redirect the image light 1032 a, 1032 b, 1032 c emitted bythe micro-displays 1030 a, 1030 b, 1030 c such that the image lightpropagates along different optical paths, in order to impinge on theappropriate associated one of the in-coupling optical element 1022 a,1022 b, 1022 c. Thus, the optical combiner 1050 combines the image light1032 a, 1032 b, 1032 c in the sense that the image light is outputtedfrom a common face of the optical combiner 1050, although light may exitthe optical combiner in slightly different directions. For example, thereflective internal surfaces 1052, 1054 of the X-cube prism may each beangled to direct the image light 1032 a, 1032 b, 1032 c along differentpaths to the eyepiece 1020. As a result, the image light 1032 a, 1032 b,1032 c may be incident on different associated ones of in-couplingoptical elements 1022 a, 1022 b, 1022 c. In some embodiments, themicro-displays 1030 a, 1030 b, 1030 c may be appropriately angledrelative to the reflective internal surfaces 1052, 1054 of the X-cubeprism to provide the desired light paths to the in-coupling opticalelements 1022 a, 1022 b, 1022 c. For example, faces of one or more ofthe micro-displays 1030 a, 1030 b, 1030 c may be angled to matchingfaces of the optical combiner 1050, such that image light emitted by themicro-displays is incident on the reflective internal surfaces 1052,1054 at an appropriate angle to propagate towards the associated incoupling optical element 1022 a, 1022 b, or 1022 c. It will beappreciated that, in addition to a cube, the optical combiner 1050 maytake the form of various other polyhedra. For example, the opticalcombiner 1050 may be in the shape of a rectangular prism having at leasttwo faces that are not squares.

With continued reference to FIG. 11A, in some embodiments, themonochrome micro-display 1030 b directly opposite the output face 1051may advantageously output green light. It will be appreciated that thereflective surfaces 1052, 1054 may have optical losses when reflectinglight from the micro-displays. In addition, the human eye is mostsensitive to the color green. Consequently, the monochrome micro-display1030 b opposite the output face 1051 preferably outputs green light, sothat the green light may proceed directly through the optical combiner1050 without needing to be reflected to be outputted from the opticalcombiner 1050. It will be appreciated, however, that the greenmonochrome micro-display may face other surfaces of the optical combiner1050 in some other embodiments.

As discussed herein, the perception of a full color image by a user maybe achieved with time division multiplexing in some embodiments. Forexample, different ones of the emissive micro-displays 1030 a, 1030 b,1030 c may be activated at different times to generate differentcomponent color images.

In such embodiments, the different component color images that form asingle full color image may be sequentially displayed sufficientlyquickly that the human visual system does not perceive the componentcolor images as being displayed at different times; that is, thedifferent component color images that form a single full color image mayall be displayed within a duration that is sufficiently short that theuser perceives the component color images as being simultaneouslypresented, rather than being temporally separated. For example, it willbe appreciated that the human visual system may have a flicker fusionthreshold. The flicker fusion threshold may be understood to a durationwithin which the human visual system is unable to differentiate imagesas being presented at different times. Images presented within thatduration are fused or combined and, as a result, may be perceived by auser to be present simultaneously. Flickering images with temporal gapsbetween the images that are outside of that duration are not combined,and the flickering of the images is perceptible. In some embodiments,the duration is 1/60 seconds or less, which corresponds to a frame rateof 60 Hz or more. Preferably, image frames for any individual eye areprovided to the user at a frame rate equal to or higher than theduration of the flicker fusion threshold of the user. For example, theframe rate for each of the left-eye or right-eye pieces may be 60 Hz ormore, or 120 Hz or more; and, as a result, the frame rate provided bythe light projection system 1010 may be 120 Hz or more, or 240 Hz ormore in some embodiments.

It will be appreciated that time division multiplexing mayadvantageously reduce the computational load on processors (e.g.,graphics processors) utilized to form displayed images. In some otherembodiments, such as where sufficient computational resources areavailable, all component color images that form a full color image maybe displayed simultaneously by the micro-displays 1030 a, 1030 b, 1030c.

As discussed herein, the micro-displays 1030 a, 1030 b, 1030 c may eachinclude arrays of light emitters. FIG. 11B illustrates an example of anarray 1042 of light emitters 1044. Where the associated micro-display isa monochrome micro-display, the light emitters 1044 may all beconfigured to emit light of the same color.

Where the associated micro-display is a full-color micro-display,different ones of the light emitters 1044 may be configured to emitlight of different colors. In such embodiments, the light emitters 1044may be considered subpixels and may be arranged in groups, with eachgroup having at least one light emitter configured to emit light of eachcomponent color. For example, where the component colors are red, green,and blue, each group may have at least one red subpixel, at least onegreen subpixel, in at least one blue subpixel.

It will be appreciated, that while the light emitters 1044 are shownarranged in a grid pattern for ease of illustration, the light emitters1044 may have other regularly repeating spatial arrangements. Forexample, the number of light emitters of different component colors mayvary, the sizes of the light emitters may vary, the shapes of the lightemitters and/or the shapes made out by groups of light emitters mayvary, etc.

With continued reference to FIG. 11B, it will be appreciated that themicro-emitters 1044 emit light. In addition, manufacturing constraints,such as lithography or other patterning and processing limitations,and/or electrical considerations, may limit how closely neighboringlight-emitters 1044 are spaced. As a result, there may be an area 1045surrounding the light-emitting emitter 1044 within which it is notpractical to form other light emitters 1044. This area 1045 forms theinter-emitter regions between light emitters 1044. In some embodiments,taking into account the area 1045, the light emitters have a pitch of,e.g., less than 10 μm, less than 8 μm, less than 6 μm, or less than 5μm, and more than 1 μm, including 1-5 μm, and an emitter size of 2 μm orless, 1.7 μm or less, or 1.3 μm or less. In some embodiments, theemitter size is within a range having an upper limit of the above-notedsizes and a lower limit of 1 μm. In some embodiments, the ratio ofemitter size to pitch is 1:1 to 1:5, 1:2 to 1:4, or 1:2 to 1:3.

It will be appreciated that, given some light emitter devicearchitectures and materials, current crowding may decrease the emitter'sefficiency and pixel droop may cause unintentional activation of pixels(e.g., due to energy directed to one light emitter bleeding into aneighboring light emitter). As a result, a relatively large area 1045may beneficially reduce current crowding and pixel droop. In someembodiments, the ratio of emitter size to pitch is preferably 1:2 to1:4, or 1:2 to 1:3.

It will also be appreciated, however, that large separations betweenlight emitters (e.g., a small light emitter to pitch ratio) mayundesirably cause visible gaps, or dark regions, between the lightemitters. In some embodiments, lens structure such as light collimatorsmay be utilized to effectively fill in these dark regions. For example,a light collimating lens may extend on and around a light emitter 1044,such that light from the emitter 1044 completely fills the lens. Forexample, the light collimating lens may have a larger width than thelight emitters 1044 and, in some embodiments, the width of thecollimating lens may be approximately equal to the pitch. As a result,the size of the emitter 1044 is effectively increased to extend acrossthe area of the lens, thereby filling in some or all of the area 1045.Lens structures such as light collimators are further discussed herein(e.g., in FIG. 30A and the related discussion).

As discussed herein, the light emitters 1044 may be OLEDs or micro-LEDs.It will be appreciated that OLEDs may utilize layers of organicmaterial, e.g., disposed between electrodes, to emit light. Micro-LEDsmay utilize inorganic materials, e.g., Group III-V materials such asGaAs, GaN, and/or GaIn for light emission. Examples of GaN materialsinclude InGaN, which may be used to form blue or green light emitters insome embodiments. Examples of GaIn materials include AlGaInP, which maybe used to form red light emitters in some embodiments. In someembodiments, the light emitters 1044 may emit light of an initial color,which may be converted to other desired colors using phosphor materialsor quantum dots. For example, the light emitter may emit blue lightwhich excites a phosphor material or quantum dot that converts the bluewavelength light to green or red wavelengths.

With reference now to FIG. 12, another example is illustrated of awearable display system with a light projection system having multipleemissive micro-displays 1030 a, 1030 b, 1030 c. The illustrated displaysystem is similar to the display system of FIG. 11A except that theoptical combiner 1050 has a standard X-cube prism configuration andincludes light redirecting structures 1080 a and 1080 c for modifyingthe angle of incidence of light on the reflective surfaces 1052, 1054 ofthe X-cube prism. It will be appreciated that a standard X-cube prismconfiguration will receive light which is normal to a face of the X-cubeand redirect this light 45° such that it is output at a normal anglefrom a transverse face of the X-cube. However, this would cause theimage light 1032 a, 1032 b, 1032 c to be incident on the samein-coupling optical element of the eyepiece 1020. In order to providedifferent paths for the image light 1032 a, 1032 b, 1032 c, so that theimage light is incident on associated ones of the in-coupling opticalelements 1022 a, 1022 b, 1022 c of the waveguide assembly, the lightredirecting structures 1080 a, 1080 c may be utilized.

In some embodiments, the light redirecting structures 1080 a, 1080 c maybe lens structures. It will be appreciated that the lens structures maybe configured to receive incident light and to redirect the incidentlight at an angle such that the light reflects off a corresponding oneof the reflective surfaces 1052, 1054 and propagates along a light pathtowards a corresponding one of the in-coupling optical elements 1022 a,1022 c. As examples, the light redirecting structures 1080 a, 1080 c maycomprise micro-lenses, nano-lenses, reflective wells, metasurfaces, andliquid crystal gratings. In some embodiments, the micro-lenses,nano-lenses, reflective wells, metasurfaces, and liquid crystal gratingsmay be organized in arrays. For example, each light emitter of themicro-displays 1030 a, 1030 c may be matched with one micro-lens. Insome embodiments, in order to redirect light in a particular direction,the micro-lens or reflective wells may be asymmetrical and/or the lightemitters may be disposed off-center relative to the micro-lens. Inaddition, in some embodiments, the light redirecting structures 1080 a,1080 c may be collimators which narrow the angular emission profiles ofassociated light emitters, to increase the amount of light ultimatelyin-coupled into the eyepiece 1020. Further details regarding such lightredirecting structures 1080 a, 1080 c are discussed below regardingFIGS. 24A-27C.

With reference now to FIG. 13A, in some embodiments, two or more of thein-coupling optical elements 1022 a, 1022 b, 1022 c may overlap (e.g.,as seen in a head-on view in the direction of light propagation into thein-coupling optical element 1022 a, 1022 b, 1022 c). FIG. 13Aillustrates an example of a side-view of a wearable display system witha light projection system 1010 having multiple emissive micro-displays1032 a, 1032 b, 1032 c and an eyepiece 1020 with overlapping lightin-coupling optical elements 1022 a, 1022 c and non-overlapping lightin-coupling optical element 1022 b. As illustrated, the in-couplingoptical elements 1022 a, 1022 c overlap, while the in-coupling opticalelements 1022 b are laterally shifted. Stated another way, thein-coupling optical elements 1022 a, 1022 c are aligned directly in thepaths of the image light 1032 a, 1032 c, while the image light 1032 bfollows another path to the eyepiece 1020, such that it is incident onan area of the eyepiece 1020 that is laterally shifted relative to thearea in which the image light 1032 a, 1032 c is incident.

As illustrated, differences between the paths for the image light 1032 band image light 1032 a, 1032 c may be established using lightredirecting structures 1080 a, 1080 c. In some embodiments, the imagelight 1032 b from the emissive micro-display 1030 b proceeds directlythrough the optical combiner 1052. The image light 1032 a from theemissive micro-display 1032 a is redirected by the light redirectingstructure 1080 a such that it reflects off of the reflective surface1054 and propagates out of the optical combiner 1050 in the samedirection as the image light 1032 c. It will be appreciated that theimage light 1032 c from the emissive micro-display 1032 c is redirectedby the light redirecting structure 1080 c such that it reflects off ofthe reflective surface 1052 at an angle such that the image light 1032 cpropagates out of the optical combiner 1050 in the same direction as theimage light 1032 b. Thus, the redirection of light by the lightredirecting structures 1080 a, 1080 c and the angles of the reflectivesurfaces 1052, 1054 are configured to provide a common path for theimage light 1032 a, 1032 c out of the optical combiner 1050, with thiscommon path being different from the path of the image light 1032 b. Insome other embodiments, one or both of the light redirecting structures1080 a, 1080 c may be omitted and the reflective surfaces 1052, 1054 inthe optical combiner 1050 may be configured to reflect the image light1032 a, 1032 c in the appropriate respective directions such that theyexit the optical combiner 1050 propagating in the same direction, whichis different from the direction of the image light 1032 b. As such,after propagating through the projection optics 1070, the image light1032 a, 1032 c exit from one exit pupil while the image light 1032 bexits from another exit pupil. In this configuration, the lightprojection system 1010 may be referred to as a two-pupil projectionsystem.

In some embodiments, the light projection system 1010 may have a singleoutput pupil and may be referred to as a single-pupil projection system.In such embodiments, the light projection system 1010 may be configuredto direct the image light 1032 a, 1032 b, 1032 c onto a single commonarea of the eyepiece 1020. Such a configuration is shown in FIG. 13B,which illustrates a wearable display system with a light projectionsystem 1010 having multiple emissive micro-displays 1030 a, 1030 b, 1030c configured to direct light to a single light in-coupling area of theeyepiece 1020. In some embodiments, as discussed further herein, theeyepiece 1020 may include a stack of waveguides having overlapping lightin-coupling optical elements. In some other embodiments, a single lightin-coupling optical element may be configured to in-couple light of allcomponent colors into a single waveguide. The display system of FIG. 13Bis similar to the display system of FIG. 13A, except for the omission ofthe light redirecting structures 1080 a, 1080 c and the use of thein-coupling optical element 1122 a and with the associated waveguide1020 a. As illustrated, the in-coupling optical element 1122 ain-couples each of image light 1032 a, 1032 b, 1032 c into the waveguide1020 a, which then relays the image light to the eye 210. In someembodiments, the in-coupling optical element 1122 a may comprise adiffractive grating. In some embodiments, the in-coupling opticalelement 1122 a is a metasurface and/or liquid crystal grating.

As discussed herein, in some embodiments, the emissive micro-displays1030 a, 1030 b, 1030 c may be monochrome micro-displays configured toemit light of different colors. In some embodiments, one or more of theemissive micro-displays 1030 a, 1030 b, 1030 c may have groups of lightemitters configured to emit light of two or more, but not all, componentcolors. For example, a single emissive micro-display may have groups oflight emitters—with at least one light emitter per group configured toemit blue light and at least one light emitter per group configured toemit green light—and a separate emissive micro-display on a differentface of the X-cube 1050 may have light emitters configured to emit redlight. In some other embodiments, the emissive micro-displays 1030 a,1030 b, 1030 c may each be full-color displays, each having lightemitters of all component colors. As noted herein, utilizing multiplesimilar micro-displays may provide advantages for dynamic range andincreased display brightness.

In some embodiments, a single full-color emissive micro-display may beutilized. FIG. 14 illustrates an example of a wearable display systemwith a single emissive micro-display 1030 b. The wearable display systemof FIG. 14 is similar to the wearable display system of FIG. 14, exceptthat the single emissive micro-display 1030 b is a full colormicro-display configured to emit light of all component colors. Asillustrated, the micro-display 1030 b emits image light 1032 a, 1032 b,1032 c of each component color. In such embodiments, the opticalcombiner 1050 (FIG. 13B) may be omitted, which may advantageously reducethe weight and size of the wearable display system relative to a systemwith an optical combiner.

As discussed above, the in-coupling optical elements of the eyepiece1020 may assume various configurations. Some examples of configurationsfor the eyepiece 1020 are discussed below in relation to FIGS. 15-23C.

FIG. 15 illustrates a side view of an example of an eyepiece 1020 havinga stack of waveguides 1020 a, 1020 b, 1020 c with overlappingin-coupling optical elements 1022 a, 1022 b, 1022 c, respectively. Itwill be appreciated that the illustrated waveguide stack may be utilizedin place of the single illustrated waveguide 1020 a of FIGS. 13B and 14.As discussed herein, each of the in-coupling optical elements 1022 a,1022 b, 1022 c is configured to in-couple light having a specific color(e.g., light of a particular wavelength, or a range of wavelengths). Inthe illustrated orientation of the eyepiece 1020 in which the imagelight propagates vertically down the page towards the eyepiece 1020, thein-coupling optical elements 1022 a, 1022 b, 1022 c are verticallyaligned with each other (e.g., along an axis parallel to the directionof propagation of the image light 1032 a, 1032 b, 1032 c) such that theyspatially overlap with each other as seen in a top down view (a head-onview in a direction of the image light 1032 a, 1032 b, 1032 cpropagating to the in-coupling optical elements).

With continued reference to FIG. 15, as discussed herein, the projectionsystem 1010 (FIGS. 13, 14) is configured to output a first monochromecolor image, a second monochrome color image, and a third monochromecolor image (e.g., red, green and blue color images) through thesingle-pupil of the projection system, the monochrome images beingformed by the image light 1032 a, 1032 b, 1032 c, respectively. Thein-coupling optical element 1022 c is configured to in-couple the imagelight 1032 c for the first color image into the waveguide 1020 c suchthat it propagates through the waveguide 1020 c by multiple totalinternal reflections at the upper and bottom major surfaces of thewaveguide 1020 c, the in-coupling optical element 1022 b is configuredto in-couple the image light 1032 b for the second color image into thewaveguide 1020 b such that it propagates through the waveguide 1020 b bymultiple total internal reflections at the upper and bottom majorsurfaces of the waveguide 1020 b, and the in-coupling optical element1022 a is configured to in-couple the image light 1032 a for the thirdcolor image into the waveguide 1020 a such that it propagates throughthe waveguide 1020 a by multiple total internal reflections at the upperand bottom major surfaces of the waveguide 1020 a.

As discussed herein, the in-coupling optical element 1022 c ispreferably configured to in-couple substantially all the incident light1032 c corresponding to the first color image into the associatedwaveguide 1020 c while allowing substantially all the incident light1032 b, 1032 a corresponding to the second color image and the thirdcolor image, respectively, to be transmitted without being in-coupled.Similarly, the in-coupling optical element 1022 b is preferablyconfigured to in-couple substantially all the incident image light 1032b corresponding to the second color image into the associated waveguide1020 b while allowing substantially all the incident light correspondingto the third color image to be transmitted without being in-coupled.

It will be appreciated that, in practice, the various in-couplingoptical elements may not have perfect selectivity. For example, some ofthe image light 1032 b, 1032 a may undesirably be in-coupled into thewaveguide 1020 c by the in-coupling optical element 1022 c; and some ofthe incident image light 1032 a may undesirably be in-coupled into thewaveguide 1020 b by the in-coupling optical element 1022 b. Furthermore,some of the image light 1032 c may be transmitted through thein-coupling optical element 1022 c and in-coupled into waveguides 1020 band/or 1020 a by the in-coupling optical elements 1020 b and/or 1020 a,respectively. Similarly, some of the image light 1032 b may betransmitted through the in-coupling optical element 1022 b andin-coupled into waveguide 1020 a by the in-coupling optical element 1022a.

In-coupling image light for a color image into an unintended waveguidemay cause undesirable optical effects, such as, for example cross-talkand/or ghosting. For example, in-coupling of the image light 1032 c forthe first color image into unintended waveguides 1020 b and/or 1020 amay result in undesirable cross-talk between the first color image, thesecond color image and/or the third color image; and/or may result inundesirable ghosting. As another example, in-coupling of the image light1032 b, 1032 a for the second or third color image, respectively, intothe unintended waveguide 1020 c may result in undesirable cross-talkbetween the first color image, the second color image and/or the thirdcolor image; and/or may cause undesirable ghosting. In some embodiments,these undesirable optical effects may be mitigated by providing colorfilters (e.g., absorptive color filters) that may reduce the amount ofincident light that is in-coupled into an unintended waveguide.

FIG. 16 illustrates a side view of an example of a stack of waveguideswith color filters for mitigating ghosting or crosstalk betweenwaveguides. The eyepiece 1020 of FIG. 16 is similar to that of FIG. 15,except for the presence of one or more of the color filters 1024 c, 1024b and 1028, 1026. The color filters 1024 c, 1024 b are configured toreduce the amount of light unintentionally in-coupled into thewaveguides 1020 b and 1020 a, respectively. The color filters 1028, 1026are configured to reduce the amount of unintentionally in-coupled imagelight which propagates through the waveguides 1020 b, 1020 c,respectively.

With continued reference to FIG. 16, a pair of color filters 1026disposed on the upper and lower major surfaces of the waveguide 1020 cmay be configured to absorb image light 1032 a, 1032 b that may havebeen unintentionally been in-coupled into waveguide 1020 c. In someembodiments, the color filter 1024 c disposed between the waveguides1020 c and 1020 b is configured to absorb image light 1032 c that istransmitted through the in-coupling optical element 1022 c without beingin-coupled. A pair of color filters 1028 disposed on the upper and lowermajor surfaces of the waveguide 1020 b is configured to absorb imagelight 1032 a that is in-coupled into waveguide 1020 b. A color filter1024 b disposed between the waveguides 1020 b and 1020 a is configuredto absorb image light 1032 b that is transmitted through the in-couplingoptical element 710.

In some embodiments, the color filters 1026 on each major surface of thewaveguide 1020 c are similar and are configured to absorb light of thewavelengths of both image light 1032 a, 1032 b. In some otherembodiments, the color filter 1026 on one major surface of the waveguide1020 c may be configured to absorb light of the color of image light1032 a, and the color filter on the other major surface may beconfigured to absorb light of the color of image light 1032 b. In eitherarrangement, the color filters 1026 may be configured to selectivelyabsorb the image light 1032 a, 1032 b propagating through the waveguide1020 c by total internal reflection. For example, at TIR bounces of theimage light 1032 a, 1032 b off the major surfaces of the waveguide 1020c, the image light 1032 a, 1032 b contacts a color filter 1026 on thosemajor surfaces and a portion of that image light is absorbed.Preferably, due to the selective absorption of image light 1032 a, 1032b by the colors filters 1026, the propagation of the in-coupled theimage light 1032 c via TIR through the waveguide 1020 c is notappreciably affected.

Similarly, the plurality of color filters 1028 may be configured asabsorption filters that absorb in-coupled image light 1032 a thatpropagates through the waveguide 1020 b by total internal reflection. AtTIR bounces of the image light 1032 a off the major surfaces of thewaveguide 1020 b, the image light 1032 a contacts a color filter 1028 onthose major surfaces and a portion of that image light is absorbed.Preferably, the absorption of the image light 1032 a is selective anddoes not affect the propagation of the in-coupled image light 1032 bthat is also propagating via TIR through the waveguide 1020 b.

With continued reference to FIG. 16, the color filters 1024 c and 1024 bmay also be configured as absorption filters. The color filter 1024 cmay be substantially transparent to light of the colors of the imagelight 1032 a, 1032 b such that the image light 1032 a, 1032 b istransmitted through the color filter 1024 c with little to noattenuation, while light of the color of the image light 1032 c isselectively absorbed. Similarly, the color filter 1024 b may besubstantially transparent to light of the color of the image light 1032a such that incident image light 1032 a is transmitted through the colorfilter 1024 b with little to no attenuation, while light of the color ofthe image light 1032 b is selectively absorbed. The color filter 1024 cmay be disposed on a major surface (e.g., the upper major surface) ofthe waveguide 1020 b as shown in FIG. 16. Alternately, the color filter1024 c may be disposed on a separate substrate positioned between thewaveguides 1020 c and 1020 b. Likewise, the color filter 1024 b may bedisposed on a major surface (e.g., an upper major surface) of thewaveguide 1020 a. Alternately, the color filter 1024 b may be disposedon a separate substrate positioned between the waveguides 1020 b and1020 a. It will be appreciated that the color filters 1024 c and 1024 bmay be vertically aligned with the single-pupil of the projector thatoutputs the image light 1032 a, 1032 b, 1032 c (in orientations wherethe image light 1032 a, 1032 b, 1032 c propagates vertically to thewaveguide stack 1020, as illustrated).

In some embodiments, the color filters 1026 and 1028 may havesingle-pass attenuation factors of less than about 10%, (e.g., less thanor equal to about 5%, less than or equal to about 2%, and greater thanabout 1%) to avoid significant undesired absorption of light propagatingthrough the thickness the waveguides 1020 c, 1020 b (e.g., light of thecolors of the image light 1032 a, 1032 b propagating through thewaveguides 1020 c, 1020 b from the ambient environment and/or otherwaveguides). Various embodiments of the color filters 1024 c and 1024 bmay be configured to have low attenuation factors for the wavelengthsthat are to be transmitted and high attenuation factor for thewavelengths that are to be absorbed. For example, in some embodiments,the color filter 1024 c may be configured to transmit greater than 80%,greater than 90%, or greater than 95%, of incident light having thecolors of the image light 1032 a, 1032 b and absorb greater than 80%,greater than 90%, or greater than 95%, of incident light having thecolor of the image light 1032 a. Similarly, the color filter 1024 b maybe configured to transmit greater than 80%, greater than 90%, or greaterthan 95%, of incident light having the color of the image light 1032 aand absorb greater than 80%, greater than 90%, or greater than 95%, ofincident light having the color of the image light 1032 b.

In some embodiments, the color filters 1026, 1028, 1024 c, 1024 b maycomprise a layer of color selective absorbing material deposited on oneor both surfaces of the waveguide 1020 c, 1020 b and/or 1020 a. Thecolor selective absorbing material may comprise a dye, an ink, or otherlight absorbing material such as metals, semiconductors, anddielectrics. In some embodiments, the absorption of material such asmetals, semiconductors, and dielectrics may be made color selective byutilizing these materials to form subwavelength gratings (e.g., agrating that does not diffract the light). The gratings may be made ofplasmonics (e.g. gold, silver, and aluminum) or semiconductors (e.g.silicon, amorphous silicon, and germanium).

The color selective material may be deposited on the substrate usingvarious deposition methods. For example, the color selective absorbingmaterial may be deposited on the substrate using jet depositiontechnology (e.g., ink-jet deposition). Ink-jet deposition may facilitatedepositing thin layers of the color selective absorbing material.Because ink-jet deposition allows for the deposition to be localized onselected areas of the substrate, ink-jet deposition provides a highdegree of control over the thicknesses and compositions of the layers ofthe color selective absorbing material, including providing fornonuniform thicknesses and/or compositions across the substrate. In someembodiments, the color selective absorbing material deposited usingink-jet deposition may have a thickness between about 10 nm and about 1micron (e.g., between about 10 nm and about 50 nm, between about 25 nmand about 75 nm, between about 40 nm and about 100 nm, between about 80nm and about 300 nm, between about 200 nm and about 500 nm, betweenabout 400 nm and about 800 nm, between about 500 nm and about 1 micron,or any value in a range/sub-range defined by any of these values).Controlling the thickness of the deposited layer of the color selectiveabsorbing material may be advantageous in achieving a color filterhaving a desired attenuation factor. Furthermore, layers havingdifferent thickness may be deposited in different portions of thesubstrate. Additionally, different compositions of the color selectiveabsorbing material may be deposited in different portions of thesubstrate using ink-jet deposition. Such variations in compositionand/or thickness may advantageously allowing for location-specificvariations in absorption. For example, in areas of a waveguide in whichtransmission of light from the ambient (to allow the viewer to see theambient environment) is not necessary, the composition and/or thicknessmay be selected to provide high absorption or attenuation of selectedwavelengths of light. Other deposition methods such as coating,spin-coating, spraying, etc. may be employed to deposit the colorselective absorbing material on the substrate.

FIG. 17 illustrates an example of a top-down view of the waveguideassemblies of FIGS. 15 and 16. As illustrated, in-coupling opticalelements 1022 a, 1022 b, 1022 c spatially overlap. In addition, thewaveguides 1020 a, 1020 b, 1020 c, along with each waveguide'sassociated light distributing element 730, 740, 750 and associatedout-coupling optical element 800, 810, 820, may be vertically aligned.The in-coupling optical elements 1022 a, 1022 b, 1022 c are configuredto in-couple incident image light 1032 a, 1032 b, 1032 c (FIGS. 15 and16), respectively, in waveguides 1020 a, 1020 b, 1020 c, respectively,such that the image light propagates towards the associated lightdistributing element 730, 740, 750 by TIR.

FIG. 18 illustrates another example of a top-down view of the waveguideassemblies of FIGS. 15 and 16. As in FIG. 17, in-coupling opticalelements 1022 a, 1022 b, 1022 c spatially overlap and the waveguides1020 a, 1020 b, 1020 c are vertically aligned. In place of eachwaveguide's associated light distributing element 730, 740, 750 andassociated out-coupling optical element 800, 810, 820, however, arecombined OPE/EPE's 1281, 1282, 1283, respectively. The in-couplingoptical elements 1022 a, 1022 b, 1022 c are configured to in-coupleincident image light 1032 a, 1032 b, 1032 c (FIGS. 15 and 16),respectively, in waveguides 1020 a, 1020 b, 1020 c, respectively, suchthat the image light propagates towards the associated combinedOPE/EPE's 1281, 1282, 1283 by TIR.

While FIGS. 15-18 show overlapping in-coupling optical elements for asingle-pupil configuration of the display system, it will be appreciatedthat the display system may have a two-pupil configuration in someembodiments. In such a configuration, where three component colors areutilized, image light for two colors may have overlapping in-couplingoptical elements, while image light for a third color may have alaterally-shifted in-coupling optical element. For example, the opticalcombiner 1050 (FIGS. 11A, 12, 13A-13B) and/or light redirectingstructures 1080 a, 1080 c may be configured to direct image lightthrough the projection optics 1070 such that image light of two colorsare incident on directly overlapping areas of the eyepiece 1020 whileanother color of the image light is incident on an area that islaterally-shifted. For example, the reflective surfaces 1052, 1054 (FIG.11A) may be angled such that image light of one color follows a commonlight path with image light from the emissive micro-display 1030 b,while image light of another color follows a different light path. Insome embodiments, rather than having both light redirecting structures1080 a, 1080 c (FIG. 12), one of these light redirecting structures maybe omitted, so that only light from one of the micro-displays 1030 a,1030 c is angled to provide a different light path from the lightemitted by the other two micro-displays.

FIG. 19A illustrates a side view of an example of an eyepiece having astack of waveguides with some overlapping and some laterally-shiftedin-coupling optical elements. The eyepiece of FIG. 19A is similar to theeyepiece of FIG. 15, except that one of the in-coupling optical elementsis laterally shifted relative to the other in-coping optical elements.In the illustrated orientation of the eyepiece 1020 in which the imagelight propagates vertically down the page towards the eyepiece 1020, thein-coupling optical elements 1022 a, 1022 c are vertically aligned witheach other (e.g., along an axis parallel to the direction of propagationof the image light 1032 a, 1032 c) such that they spatially overlap witheach other as seen in a head-on view in a direction of the image light1032 a, 1032 c propagating to the in-coupling optical elements 1022 a,1022 b, 1022 c. As seen in the same head-on view (e.g., as seen in atop-down view in the illustrated orientation), the in-coupling opticalelement 1022 b is shifted laterally relative to the other in-couplingoptical elements 1022 a, 1022 c. Light for the in-coupling opticalelement 1022 b is output to the eyepiece 1020 through a different exitpupil than light for the in-coupling optical elements 1022 a, 1022 c. Itwill be appreciated that the illustrated waveguide stack comprising thewaveguides 1020 a, 1020 b, 1020 c may be utilized in place of the singleillustrated waveguide 1020 a of FIGS. 13 and 14.

With continued reference to FIG. 19, the in-coupling optical element1022 c is configured to in-couple the image light 1032 c into thewaveguide 1020 c such that it propagates through the waveguide 1020 c bymultiple total internal reflections between the upper and bottom majorsurfaces of the waveguide 1020 c, the in-coupling optical element 1022 bis configured to in-couple the image light 1032 b into the waveguide1020 b such that it propagates through the waveguide 1020 b by multipletotal internal reflections between the upper and bottom major surfacesof the waveguide 1020 b, and the in-coupling optical element 1022 a isconfigured to in-couple the image light 1032 a into the waveguide 1020 asuch that it propagates through the waveguide 1020 a by multiple totalinternal reflections between the upper and bottom major surfaces of thewaveguide 1020 a.

The in-coupling optical element 1022 c is preferably configured toin-couple all the incident light 1032 c into the associated waveguide1020 c while being transmissive to all the incident light 1032 a. On theother hand, the image light 1032 b may propagate to the in-couplingoptical element 1022 b without needing to propagate through any otherin-coupling optical elements. This may be advantageous in someembodiments by allowing light, to which the eye is more sensitive, to beincident on a desired in-coupling optical element without any loss ordistortion associated with propagation through other in-coupling opticalelements. Without being limited by theory, in some embodiments, theimage light 1032 b is green light, to which the human eye is moresensitive. It will be appreciated that, while the waveguides 1020 a,1020 b, 1020 c are illustrated arranged a particular order, in someembodiments, the order of the waveguides 1020 a, 1020 b, 1020 c maydiffer.

It will be appreciated that, as discussed herein, the in-couplingoptical element 1022 c overlying the in-coupling optical elements 1022 amay not have perfect selectivity. Some of the image light 1032 a mayundesirably be in-coupled into the waveguide 1020 c by the in-couplingoptical element 1022 c; and some of the image light 1032 c may betransmitted through the in-coupling optical element 1022 c, after whichthe image light 1032 c may strike the in-coupling optical element 1020 aand be in-coupled into the waveguide 1020 a. As discussed herein, suchundesired in-coupling may be visible as ghosting or crosstalk.

FIG. 19B illustrates a side view of an example of the eyepiece of FIG.19A with color filters for mitigating ghosting or crosstalk betweenwaveguides. In particular, color filters 1024 c and/or 1026 are added tothe structures shown in FIG. 19A. As illustrated, the in-couplingoptical element 1022 c may unintentionally in-couple a portion of theimage light 1032 a into the waveguide 1020 c. In addition, oralternatively, a portion of the image light 1032 c undesirably betransmitted through the in-coupling optical element 1022 c after whichit may unintentionally be in-coupled by the in-coupling optical element1022 a.

To mitigate unintentionally in-couple image light 1032 a propagatingthrough the waveguide 1022 c, absorptive color filters 1026 may beprovided on one or both major surfaces of the waveguide 1022 c. Theabsorptive color filters 1026 may be configured to absorb light of thecolor of the unintentionally in-coupled image light 1032 a. Asillustrated, the absorptive color filters 1026 are disposed in thegeneral direction of propagation of the image light through thewaveguide 1020 c. Thus, the absorptive color filters 1026 are configuredto absorb image light 1032 a as that light propagates through thewaveguide 1020 c by TIR and contacts the absorptive color filters 1026while reflecting off one or both of the major surfaces of the waveguide1020 c.

With continued reference to FIG. 19B, to mitigate image light 1032 cwhich propagates through the in-coupling optical element 1022 c withoutbeing in-coupled, the absorptive color filter 1024 c may be providedforward of the in-coupling optical element 1022 a. The absorptive colorfilter 1024 c is configured to absorb light of the color of the imagelight 1032 c, to prevent that light from propagating to the in-couplingoptical element 1022 a. While illustrated between the waveguides 1020 cand 1020 b, in some other embodiments, the absorptive color filter 1024c may be disposed between the waveguides 1020 b and 1020 a. It will beappreciated that further details regarding the composition, formation,and properties of the absorptive color filters 1024 c and 1026 areprovided in the discussion of FIG. 16.

It will also be appreciated that in the embodiments illustrated in FIGS.16 and 19B, one or more of the color filters 1026, 1028, 1024 c, and1024 b may be omitted if one or more in-coupling optical elements 1022a, 1022 b, 1022 c have sufficiently high selectivity for the color ofthe light that is intended to be in-coupled into the associatedwaveguide 1020 a, 1020 b, 1022 c, respectively.

FIG. 20A illustrates an example of a top-down view of the eyepieces ofFIGS. 19A and 19B. As illustrated, in-coupling optical elements 1022 a,1022 c spatially overlap, while in-coupling optical element 1022 b islaterally-shifted. In addition, the waveguides 1020 a, 1020 b, 1020 c,along with each waveguide's associated light distributing element 730,740, 750 and associated out-coupling optical element 800, 810, 820, maybe vertically aligned. The in-coupling optical elements 1022 a, 1022 b,1022 c are configured to in-couple incident image light 1032 a, 1032 b,1032 c (FIGS. 15 and 16), respectively, in waveguides 1020 a, 1020 b,1020 c, respectively, such that the image light propagates towards theassociated light distributing element 730, 740, 750 by TIR.

FIG. 20B illustrates another example of a top-down view of the waveguideassembly of FIGS. 19A and 19B. As in FIG. 20A, in-coupling opticalelements 1022 a, 1022 c spatially overlap, the in-coupling opticalelement is laterally-shifted, and the waveguides 1020 a, 1020 b, 1020 care vertically aligned. In place of each waveguide's associated lightdistributing element 730, 740, 750 and associated out-coupling opticalelement 800, 810, 820, however, are combined OPE/EPE's 1281, 1282, 1283,respectively. The in-coupling optical elements 1022 a, 1022 b, 1022 care configured to in-couple incident image light 1032 a, 1032 b, 1032 c(FIGS. 15 and 16), respectively, in waveguides 1020 a, 1020 b, 1020 c,respectively, such that the image light propagates towards theassociated combined OPE/EPE's 1281, 1282, 1283 by TIR.

With reference now to FIG. 21, it will be appreciated that re-bounce ofin-coupled light may undesirably occur in waveguides. Re-bounce occurswhen in-coupled light propagating along a waveguide strikes thein-coupling optical element a second or subsequent time after theinitial in-coupling incidence. Re-bounce may result in a portion of thein-coupled light being undesirably out-coupled and/or absorbed by amaterial of the in-coupling optical element. The out-coupling and/orlight absorption undesirably may cause a reduction in overallin-coupling efficiency and/or uniformity of the in-coupled light.

FIG. 21 illustrates a side view of an example of re-bounce in awaveguide 1030 a. As illustrated, image light 1032 a is in-coupled intothe waveguide 1030 a by in-coupling optical element 1022 a. In-couplingoptical element 1022 a redirects the image light 1032 a such that itgenerally propagates through the waveguide in the direction 1033.Re-bounce may occur when in-coupled image light internally reflects orbounces off a major surface of the waveguide 1030 a opposite thein-coupling optical element 1022 a and is incident on or experiences asecond bounce (a re-bounce) at the in-coupling optical element 1022 a.The distance between two neighboring bounces on the same surface of thewaveguide 1030 a is indicated by spacing 1034.

Without being limited by theory, it will be appreciated that thein-coupling optical element 1022 a may behave symmetrically; that is, itmay redirect incident light such that the incident light propagatesthrough the waveguide at TIR angles. However, light that is incident onthe diffractive optical elements at TIR angles (such as upon re-bounce)may also be out-coupled. In addition or alternatively, in embodimentswhere the in-coupling optical element 1022 a is coated with a reflectivematerial, it will be understood that the reflection of light off of alayer of material such as metal may also involve partial absorption ofthe incident light, since reflection may involve the absorption andemission of light from a material. As a result, light out-couplingand/or absorption may undesirably cause loss of in-coupled light.Accordingly, re-bounced light may incur significant losses, as comparedwith light that interacts only once with the in-coupling optical element1022 a.

In some embodiments, the in-coupling elements are configured to mitigatein-coupled image light loss due to re-bounce. Generally, re-bounce ofin-coupled light occurs towards the end 1023 of the in-coupling opticalelement 1022 a in the propagation direction 1033 of the in-coupledlight. For example, light in-coupled at the end of the in-couplingoptical element 1022 a opposite the end 1023 may re-bounce if thespacing 1034 for that light is sufficiently short. To avoid suchre-bounce, in some embodiments, the in-coupling optical element 1022 ais truncated at the propagation direction end 1023, to reduce the width1022 w of the in-coupling optical element 1022 a along which re-bounceis likely to occur. In some embodiments, the truncation may be acomplete truncation of all structures of the in-coupling optical element1022 a (e.g., the metallization and diffractive gratings). In some otherembodiments, for example, where the in-coupling optical element 1022 acomprises a metalized diffraction grating, a portion of the in-couplingoptical element 1022 a at the propagation direction end 1023 may not bemetalized, such that the propagation direction end 1023 of thein-coupling optical element 1022 a absorbs less re-bouncing light and/oroutcouples re-bouncing light with a lower efficiency. In someembodiments, a diffractive region of an in-coupling optical element 1022a may have a width along a propagation direction 1033 shorter than itslength perpendicular to the propagation direction 1033, and/or may besized and shaped such that a first portion of image light 1032 a isincident on the in-coupling optical element 1022 a and a second portionof the beam of light impinges on the waveguide 1030 a without beingincident on the in-coupling optical element 1022 a. While waveguide 1032a and light in-coupling optical element 1022 a are illustrated alone forclarity, it will be appreciated that re-bounce and the strategiesdiscussed for reducing re-bounce may apply to any of the in-couplingoptical elements disclosed herein. It will also be appreciated that thespacing 1034 is related to the thickness of the waveguide 1030 a (alarger thickness results in a larger spacing 1034). In some embodiments,the thickness of individual waveguides may be selected to set thespacing 1034 such that re-bounce does not occur. Further detailsregarding re-bounce mitigation may be found in U.S. ProvisionalApplication No. 62/702,707, filed on Jul. 24, 2018, the entiredisclosure of which is incorporated by reference herein.

FIGS. 22A-23C illustrate examples of top-down views of an eyepiecehaving in-coupling optical elements configured to reduce re-bounce.In-coupling optical element 1022 a, 1022 b, 1022 c are configured toin-couple light such that it propagates in a propagation directiontowards the associated light distributing elements 730, 740, 750 (FIGS.22A-22C) or combined OPE/EPE's 1281, 1282, 1283 (FIGS. 23A-23C). Asillustrated, the in-coupling optical element 1022 a, 1022 b, 1022 c mayhave a shorter dimension along the propagation direction and a longerdimension along the transverse axis. For example, the in-couplingoptical element 1022 a, 1022 b, 1022 c may each be in the shape of arectangle with a shorter side along the axis of the propagationdirection and a longer side along an orthogonal axis. It will beappreciated that the in-coupling optical elements 1022 a, 1022 b, 1022 cmay have other shapes (e.g., orthogonal, hexagonal, etc.). In addition,different ones of the in-coupling optical elements 1022 a, 1022 b, 1022c may have different shapes in some embodiments. Also, preferably, asillustrated, non-overlapping in-coupling optical elements may bepositioned such that they are not in the propagation direction of otherin-coupling optical elements. For example, as shown in FIGS. 22A, 22B,23A, and 23B, the non-overlapping in-coupling optical elements may bearranged in a line along an axis crossing (e.g., orthogonal to) the axisof the propagation direction.

It will be appreciated that in the waveguide assemblies of FIGS. 22A-22Care similar, except for the overlap of the in-coupling optical elements1022 a, 1022 b, 1022 c. For example, FIG. 22A illustrates in-couplingoptical elements 1022 a, 1022 b, 1022 c with no overlap. FIG. 22Billustrates overlapping in-coupling optical elements 1022 a, 1022 c, andnon-overlapping in-coupling optical elements 1022 b. FIG. 22Cillustrates overlap between all the in-coupling optical elements 1022 a,1022 b, 1022 c.

The waveguide assemblies of FIGS. 23A-23C are also similar, except forthe overlap of the in-coupling optical elements 1022 a, 1022 b, 1022 c.FIG. 23A illustrates in-coupling optical elements 1022 a, 1022 b, 1022 cwith no overlap. FIG. 23B illustrates overlapping in-coupling opticalelements 1022 a, 1022 c, and non-overlapping in-coupling opticalelements 1022 b. FIG. 22C illustrates overlap between all thein-coupling optical elements 1022 a, 1022 b, 1022 c.

With reference now to FIG. 24A, it will be appreciated that the emissivemicro-displays have high etendue, which presents a challenge forefficient light utilization. As discussed herein, the emissivemicro-displays may include a plurality of individual light emitters.Each of these light emitters may have a large angular emission profile,e.g., a Lambertian or near-Lambertian emission profile. Undesirably, notall of this light may be captured and directed to the eyepiece of thedisplay system.

FIG. 24A illustrates an example of angular emission profiles of lightemitted by individual light emitters 1044 of an emissive micro-display1032, and light captured by projection optics 1070. The illustratedemissive micro-display 1032 may correspond to any of theemissive-micro-displays disclosed herein, including the emissivemicro-displays 1032 a, 1032 b, 1032 c. As illustrated, the projectionoptics 1070 may be sized such that it will capture light having anangular emission profile 1046. However, the angular emission profiles1046 in the light emitters 1044 is significantly larger; not all of thelight emitted by the light emitters 1044 will be incident on theprojection optics 1070, nor necessarily incident at angles at which thelight will propagate into and through the projection optics 1070. As aresult, some of the light emitted by the light emitter 1044 mayundesirably be “wasted” since it is not captured and ultimately relayedto the user's eye to form images. This may result in images that appeardarker than would be expected if more of the light outputted by thelight emitters 1040 ultimately reached the user's eye.

In some embodiments, one strategy for capturing more of the lightemitted by the light emitters 1040 is to increase the size of theprojection optics 1070, to increase the size of the numerical apertureof the projection optics 1070 capturing light. In addition oralternatively, the projection optics 1070 may also be formed with highrefractive index materials (e.g., having refractive indices above 1.5)which may also facilitate light collection. In some embodiments, theprojection optics 1070 may utilize a lens sized to capture a desired,high proportion of the light emitted by the light emitters 1044. In someembodiments, the projection optics 1070 may be configured to have anelongated exit pupil, e.g., to emit light beams having a cross-sectionalprofile similar to the shapes of the in-coupling optical elements 1022a, 1022 b, 1022 c of FIGS. 22A-23C. For example, the projection optics1070 may be elongated in a dimension corresponding to the elongateddimension of the in-coupling optical elements 1022 a, 1022 b, 1022 c ofFIGS. 22A-23C. Without being limited by theory, such elongatedin-coupling optical elements 1022 a, 1022 b, 1022 c may improve theetendue mismatch between the emissive micro-display and the eyepiece1020 (FIGS. 22A-23C). In some embodiments, the thickness of thewaveguides of the eyepiece 1020 (e.g., FIGS. 11A, and 12-23C) may beselected to increase the percentage of light effectively captured, e.g.,by reducing re-bounce by increasing the re-bounce spacing, as discussedherein.

In some embodiments, one or more light collimators may be utilized toreduce or narrow the angular emission profile of light from the lightemitters 1044. As a result, more of the light emitted by the lightemitters 1044 may be captured by the projection optics 1070 and relayedto the eyes of a user, advantageously increasing the brightness ofimages and the efficiency of the display system. In some embodiments,the light collimators may allow the light collection efficiency of theprojection optics (the percentage of light emitted by the light emitters1044 that is captured by the projection optics) to reach values of 80%or more, 85% or more, or 90% or more, including about 85-95% or 85-90%.In addition, the angular emission profile of the light from the lightemitters 1044 may be reduced to 60° or less, 50° or less, or 40° or less(from, e.g., 180°). In some embodiments, the reduced angular emissionprofiles may be in the range of about 30-60°, 30-50°, or 30-40°. It willbe appreciated that light from the light emitters 1044 may make out theshape of a cone, with the light emitter 1044 at the vertex of the cone.The angular mission profile refers to the angle made out by the sides ofthe cone, with the associated light emitter 1044 at the vertex of theangle (as seen in a cross-section taken along a plane extending throughthe middle of the cone and including the cone apex).

FIG. 24B illustrates an example of the narrowing of angular emissionprofiles using an array of light collimators. As illustrated, theemissive micro-display 1032 includes an array of light emitters 1044,which emit light with an angular emission profile 1046. An array 1300 oflight collimators 1302 is disposed forward of the light emitters 1044.In some embodiments, each light emitter 1044 is matched 1-to-1 with anassociated light collimator 1302 (one light collimator 1302 per lightemitter 1044). Each light collimator 1302 redirects incident light fromthe associated light emitter 1044 to provide a narrowed angular emissionprofiles 1047. Thus, the relatively large angular emission profiles 1046are narrowed to the smaller angular emission profiles 1047.

In some embodiments, the light collimators 1302 and array 1300 may bepart of the light redirecting structures 1080 a, 180 c of FIGS. 12 and13A. Thus, light collimators 1302 may narrow the angular emissionprofile of the light emitters 1044 and also redirect the light such thatit propagates into the optical combiner 1050 at the appropriate anglesto define multiple light paths and the related multiple exit pupils. Itwill be appreciated that light may be redirected in particulardirections by appropriately shaping the light collimators 1302.

Preferably, the light collimators 1302 are positioned in tight proximityto the light emitters 1044 to capture a large proportion of the lightoutputted by the light emitters 1044. In some embodiments, there may bea gap between the light collimators 1302 and the light emitters 1044. Insome other embodiments, the light collimator 1302 may be in contact withthe light emitters 1044. It will be appreciated that the angularemission profile 1046 may make out a wide cone of light. Preferably, theentirety or majority of a cone of light from a light emitter 1044 isincident on a single associated light collimator 1302. Thus, in someembodiments, each light emitter 1044 is smaller (occupies a smallerarea) than the light receiving face of an associated light collimator1302. In some embodiments, each light emitter 1044 has a smaller widththan the spacing between neighboring far light emitters 1044.

Advantageously, the light collimators 1302 may increase the efficiencyof the utilization of light and may also reduce the occurrence ofcrosstalk between neighboring light emitters 1044. It will beappreciated that crosstalk between light emitters 1044 may occur whenlight from a neighboring light emitter is captured by a light collimator1302 not associated with that neighboring light emitter. That capturedlight may be propagated to the user's eye, thereby providing erroneousimage information for a given pixel.

With reference to FIGS. 24A and 24B, the size of the beam of lightcaptured by the projection optics 1070 may influence the size of thebeam of light which exits the projection optics 1070. As shown in FIG.24A, without the use light collimators, the exit beam may have arelatively large width 1050. As shown in FIG. 24B, with lightcollimators 1302, the exit beam may have a smaller width 1052. Thus, insome embodiments, the light collimators 1302 may be used to provide adesired beam size for in-coupling into an eyepiece. For example, theamount that the light collimators 1302 narrow the angular emissionprofile 1046 may be selected based at least partly upon the size of theintra-coupling optical elements in the eyepiece to which the lightoutputted by the projection optics 1070 is directed.

It will be appreciated that the light collimators 1302 may take variousforms. For example, the light collimators 1302 may be micro-lenses orlenslets, in some embodiments. As discussed herein, each micro-lenspreferably has a width greater than the width of an associated lightemitter 1044. The micro-lenses may be formed of curved transparentmaterial, such as glass or polymers, including photoresist and resinssuch as epoxy. In some embodiments, light collimators 1302 may benano-lenses, e.g., diffractive optical gratings. In some embodiments,light collimators 1302 may be metasurfaces and/or liquid crystalgratings. In some embodiments, light collimator's 1302 may take the formof reflective wells.

It will be appreciated that different light collimators 1302 may havedifferent dimensions and/or shapes depending upon the wavelengths orcolors of light emitted by the associated light emitter 1044. Thus, forfull-color emissive micro-displays, the array 1300 may include aplurality of light collimators 1302 with different dimensions and/orshapes depending upon the color of light emitted by the associate lightemitter 1044. In embodiments where the emissive micro-display is amonochrome micro-display, the array 1300 may be simplified, with each ofthe light collimators 1302 in the array being configured to redirectlight of the same color. With such monochrome micro-displays, the lightcollimator 1302 may be similar across the array 1300 in someembodiments.

With continued reference to FIG. 24B, as discussed herein, the lightcollimators 1302 may have a 1-to-1 association with the light emitters1044. For example, each light emitter 1044 may have a discreteassociated light collimator 1302. In some other embodiments, lightcollimators 1302 may be elongated such that they extend across multiplelight emitters 1044. For example, in some embodiments, the lightcollimator 1302 may be elongated into the page and extend in front of arow of multiple light emitters 1044. In some other embodiments, a singlelight collimator 1302 may extend across a column of light emitters 1044.In yet other embodiments, the light collimator 1302 may comprise stackedcolumns and/or rows of lens structures (e.g., nano-lens structures,micro-lens structures, etc.).

As noted above, the light collimators 1302 may take the form ofreflective wells. FIG. 25A illustrates an example of a side view of anarray of tapered reflective wells for directing light to projectionoptics. As illustrated, the light collimator array 1300 may include asubstrate 1301 in which a plurality of light collimators 1302, in theform of reflective wells, may be formed. Each well may include at leastone light emitter 1044, which may emit light with a Lambertian angularemission profile 1046. The reflective walls 1303 of the wells of thelight collimators 1302 are tapered and reflect the emitted light suchthat it is outputted from the well with a narrower angular emissionprofile 1047. As illustrated, reflective walls 1303 may be tapered suchthat the cross-sectional size increases with distance from the lightemitter 1044. In some embodiments, the reflective walls 1303 may becurved. For example, the sides 1303 may have the shape of a compoundparabolic concentrator (CPC).

With reference now to FIG. 25B, an example of a side view of anasymmetric tapered reflective well is illustrated. As discussed herein,e.g., as illustrated in FIGS. 12A-13A, it may be desirable to utilizethe light collimators 1302 to steer light in a particular direction notnormal to the surface of the light emitter 1044. In some embodiments, asviewed in a side view such as illustrated in FIG. 25B, the lightcollimator 1302 may be asymmetric, with the upper side 1303 a forming adifferent angle (e.g., a larger angle) with the surface of the lightemitter 1044 than the lower side 1303 b; for example, the angles of thereflective walls 1303 a, 1303 b relative to the light emitter 1044 maydiffer on different sides of the light collimators 1302 in order todirect the light in the particular non-normal direction. Thus, asillustrated, light exiting the light collimator 1302 may propagategenerally in a direction 1048 which is not normal to the surface of thelight emitter 1044. In some other embodiments, in order to direct lightin the direction 1048, the taper of the upper side 1303 a may bedifferent than the taper of the lower side; for example, the upper side1303 a may flare out to a greater extent than the lower side 1303 b.

With continued reference to FIG. 25, the substrate 1301 may be formed ofvarious materials having sufficient mechanical integrity to maintain thedesired shape of the reflective walls 1303. Examples of suitablematerials include metals, plastics, and glasses. In some embodiments,the substrate 1301 may be a plate of material. In some embodiments,substrate 1301 is a continuous, unitary piece of material. In some otherembodiments, the substrate 1301 may be formed by joining together two ormore pieces of material.

The reflective walls 1303 may be formed in the substrate 1301 by variousmethods. For example, the walls 1303 may be formed in a desired shape bymachining the substrate 1301, or otherwise removing material to definethe walls 1303. In some other embodiments, the walls 1303 may be formedas the substrate 1301 is formed. For example, the walls 1303 may bemolded into the substrate 1301 as the substrate 1301 is molded into itsdesired shape. In some other embodiments, the walls 1303 may be definedby rearrangement of material after formation of the body 2200. Forexample, the walls 1303 may be defined by imprinting.

Once the contours of the walls 1303 are formed, they may undergo furtherprocessing to form surfaces having the desired degree of reflection. Insome embodiments, the surface of the substrate 1301 may itself bereflective, e.g., where the body is formed of a reflective metal. Insuch cases, the further processing may include smoothing or polishingthe interior surfaces of the walls 1303 to increase their reflectivity.In some other embodiments, the interior surfaces of the reflectors 2110may be lined with a reflective coating, e.g., by a vapor depositionprocess. For example, the reflective layer may be formed by physicalvapor deposition (PVD) or chemical vapor deposition (CVD).

It will be appreciated that the location of a light emitter relative toan associated light collimator may influence the direction of emittedlight out of the light collimator. This is illustrated, for example, inFIGS. 26A-26C, which illustrate examples of differences in light pathsfor light emitters at different positions relative to center lines ofoverlying, associated light collimators. As shown in FIG. 26A, theemissive micro-display another 30 has a plurality of light emitters 1044a, each having an associated light collimator 1302 which facilitates theoutput of light having narrowed angular emission profiles 1047. Thelight passes through the projection optics 1070 (represented as a simplelens for ease of illustration), which converges the light from thevarious light emitters 1044 a onto an area 1402 a.

With continued reference to FIG. 26A, in some embodiments, each of thelight collimators 1302 may be symmetric and may have a center line whichextends along the axis of symmetry of the light collimator. In theillustrated configuration, the light emitters 1044 a are disposed on thecenter line of each of the light collimators 1302.

With reference now to FIG. 26B, light emitters 1044 b are offset by adistance 1400 from the center lines of their respective lightcollimators 1302. This offset causes light from the light emitters 1044b to take a different path through the light collimators 1302, whichoutput light from the light emitters 1044 b with narrowed angularemission profiles 1047 b. The projection optics 1070 then converges thelight from the light emitters 1044 b onto the area 1402 b, which isoffset relative to the area 1402 a on which light from the lightemitters 1044 a converge.

With reference now to FIG. 26C, light emitters 1044 c offset from boththe light emitters 1044 a and 1044 b are illustrated. This offset causeslight from the light emitters 1044 c to take a different path throughthe light collimators 1302 than light from the light emitters 1044 a and1044 b. This causes the light collimators 1302 to output light from thelight emitters 1044 c with narrowed angular emission profiles that takea different path to the projection optics 1070 than the light from thelight emitters 1044 a and 1044 b. Ultimately, the projection optics 1070converges the light from the light emitters 1044 c onto the area 1402 c,which is offset relative to the areas 1402 a and 1402 b.

With reference to FIGS. 26A-26C, each triad of light emitters 1044 a,1044 b, 1044 c may share a common light collimator 1302. In someembodiments, the micro-display 1030 may be a full-color micro-displayand each light emitter 1044 a, 1044 b, 1044 c may be configured to emitlight of a different component color. Advantageously, the offset areas1402 a, 1402 b, 1402 c may correspond to the in-coupling opticalelements of a waveguide in some embodiments. For example, the areas 1402a, 1402 b, 1402 c may correspond to the in-coupling optical element 1022a, 1022 b, 1022 c, respectively, of FIGS. 11A and 12. Thus, the lightcollimators 1302 and the offset orientations of the light emitters 1044a, 1044 b, 1044 c may provide an advantageously simple three-pupilprojection system 1010 using a full-color emissive micro-display.

As noted herein, the light collimator 1302 may also take the form of anano-lens. FIG. 27 illustrates an example of a side view of individuallight emitters 1044 of an emissive micro-display 1030 with an overlyingarray 1300 of light collimators 1302 which are nano-lenses. As discussedherein, individual ones of the light emitters 1044 may each have anassociated light collimator 1302. The light collimators 1302 redirectlight from the light emitters 1044 to narrow the large angular emissionprofile 1046 of the light emitters 1044, to output light with thenarrowed angular emission profile 1047.

With continued reference to FIG. 27, in some embodiments, the lightcollimators 1302 may be grating structures. In some embodiments, thelight collimators 1302 may be gratings formed by alternating elongateddiscrete expanses (e.g., lines) of material having different refractiveindices. For example, expanses of material 1306 may be elongated intoand out of the page and may be formed in and separated by material ofthe substrate 1308. In some embodiments, the elongated expanses ofmaterial 1306 may have sub-wavelength widths and pitch (e.g., widths andpitch that are smaller than the wavelengths of light that the lightcollimators 1302 are configured to receive from the associated lightemitters 1044). In some embodiments, the pitch 1304 may be 30-300 nm,the depth of the grating may be 10-1000 nm, the refractive index of thematerial forming the substrate 1308 may be 1.5-3.5, and the refractiveindex of the material forming the grating features 1306 may be 1.5-2.5(and different from the refractive index of the material forming thesubstrate 1308).

The illustrated grating structure may be formed by various methods. Forexample, the substrate 1308 may be etched or nano-imprinted to definetrenches, and the trenches may be filled with material of a differentrefractive index from the substrate 1308 to form the grating features1306.

Advantageously, nano-lens arrays may provide various benefits. Forexample, the light collection efficiencies of the nano-lenslets may belarge, e.g., 80-95%, including 85-90%, with excellent reductions inangular emission profiles, e.g., reductions to 30-40° (from 180°). Inaddition, low levels of cross-talk may be achieved, since each of thenano-lens light collimators 1302 may have physical dimensions andproperties (e.g., pitch, depth, the refractive indices of materialsforming the feature 1306 and substrate 1308) selected to act on light ofparticular colors and possibly particular angles of incidence, whilepreferably providing high extinction ratios (for wavelengths of light ofother colors). In addition, the nano-lens arrays may have flat profiles(e.g., be formed on a flat substrate), which may facilitates integrationwith micro-displays that may be flat panels, and may also facilitatemanufacturing and provide high reproducibility and precision in formingthe nano-lens array. For example, highly reproducible trench formationand deposition processes may be used to form each nano-lens. Moreover,these processes allow, with greater ease and reproducibility, forvariations between nano-lenses of an array than are typically achievedwhen forming curved lens with similar variations.

With reference now to FIG. 28, a perspective view of an example of anemissive micro-display 1030 is illustrated. It will be appreciated thatthe light collimator arrays 1300 advantageously allow light emitted froma micro-display to be routed as desired. As result, in some embodiments,the light emitters of a full-color micro-display may be organized asdesired, e.g., for ease of manufacturing or implementation in thedisplay device. In some embodiments, the light emitters 1044 may bearranged in rows or columns 1306 a, 1306 b, 1306 c. Each row or columnmay include light emitters 1044 configured to emit light of the samecomponent color. In displays where three component colors are utilized,there may be groups of three rows or columns which repeat across themicro-display 1030. It will be appreciated that where more componentcolors are utilized, each repeating group may have that number of rowsor columns. For example, where four component colors are utilized, eachgroup may have four rows or four columns, with one row or one columnformed by light emitters configured to emit light of a single componentcolor.

In some embodiments, some rows or columns may be repeated to increasethe number of light emitters of a particular component color. Forexample, light emitters of some component colors may occupy multiplerows or columns. This may facilitate color balancing and/or may beutilized to address differential aging or reductions in light emissionintensity over time.

With reference to FIGS. 27 and 28, in some embodiments, the lightemitters 1044 may each have an associated light collimator 1302. In someother embodiments, each line 1306 a, 1306 b, 1306 c of multiple lightemitters 1044 may have a single associated light collimator 1302. Thatsingle associated light collimator 1302 may extend across substantiallythe entirety of the associated line 1306 a, 1306 b, or 1306 c. In someother embodiments, the associated light collimator 1302 may be elongatedand extend over a plurality of light emitters 1044 forming a portion ofan associated line 1306 a, 1306 b, or 1306 c, and multiple similar lightcollimators 1302 may be provided along each of the associated lines 1306a, 1306 b, 1306 c.

With continued reference to FIG. 28, each light emitter 1044 may beelongated along a particular axis (e.g., along the y-axis asillustrated); that is, each light emitter has a length along theparticular axis, the length being longer than a width of the lightemitter. In addition, a set of light emitters configured to emit lightof the same component color may be arranged in a line 1306 a, 1306 b, or1306 c (e.g. a row or column) extending along an axis (e.g., the x-axis)which crosses (e.g., is orthogonal to) the light emitter 1044's elongateaxis. Thus, in some embodiments, light emitters 1044 of the samecomponent color form a line 1306 a, 1306 b, or 1306 c of light emitters,with the line extending along a first axis (e.g., the x-axis), and withindividual light emitters 1044 within the line elongated along a secondaxis (e.g., the y-axis).

In contrast, it will be appreciated that full-color micro-displaytypically include sub-pixels of each component color, with thesub-pixels arranged in particular relatively closely-packed spatialorientations in groups, with these groups reproduced across an array.Each group of sub-pixels may form a pixel in an image. In some cases,the sub-pixels are elongated along an axis, and rows or columns ofsub-pixels of the same component color extent along that same axis. Itwill be appreciated that such an arrangement allows the sub-pixels ofeach group to be located close together, which may have benefits forimage quality and pixel density. In the illustrated arrangement of FIG.28, however, sub-pixels of different component colors are relatively farapart, due to the elongate shape of the light emitters 1044; that is,the light emitters of the line 1306 a are relatively far apart from thelight emitters of the line 1306 c since the elongated shape of the lightemitters of the line 1306 b causes the light emitters 1306 a and 1306 cto be spaced out more than neighboring light emitters of a given line oflight emitters. While this may be expected to provide unacceptably poorimage quality if the image formed on the surface of the micro-display1030 was directly relayed to a user's eye, the use of the lightcollimator array 1300 advantageously allows light of different colors tobe routed as desired to form a high quality image. For example, light ofeach component color may be used to form separate monochrome imageswhich are then routed to and combined in an eyepiece, such as theeyepiece 1020 (e.g., FIGS. 11A and 12-14).

With reference to FIGS. 27 and 28, in some embodiments, the lightemitters 1044 may each have an associated light collimator 1302. In someother embodiments, each line 1306 a, 1306 b, 1306 c of light emitters1044 may have a single associated light collimator 1302. That singleassociated light collimator 1302 may extend across substantially theentirety of the associated line 1306 a, 1306 b, or 1306 c. In some otherembodiments, the associated light collimator 1302 may be elongated andextend over a plurality of light emitters 1044 forming a portion of anassociated line 1306 a, 1306 b, or 1306 c, and multiple similar lightcollimators 1302 may be provided along each of the associated lines 1306a, 1306 b, 1306 c.

It will be appreciated that the light collimators 1302 may be utilizedto direct light along different light paths to form multi-pupilprojections systems. For example, the light collimators 1302 may directlight of different component colors to two or three areas, respectively,for light in-coupling.

FIG. 29 illustrates an example of a wearable display system with thefull-color emissive micro-display 1030 of FIG. 28 used to form amulti-pupil projection system 1010. In the illustrated embodiment, thefull-color emissive micro-display 1030 emits light of three componentcolors and forms a three-pupil projection system 1010. The projectionsystem 1010 has three exit pupils through which image light 1032 a, 1032b, 1032 c of different component colors propagates to threelaterally-shifted light in-coupling optical elements 1022 a, 1022 b,1022 c, respectively, of an eyepiece 1020. The eyepiece 1020 then relaysthe image light 1032 a, 1032 b, 1032 c to the eye 210 of a user.

The emissive-micro-display 1030 includes an array of light emitters1044, which may be subdivided into monochrome light emitters 1044 a,1044 b, 1044 c, which emit the image light 1032 a, 1032 b, 1032 c,respectively. It will be appreciated that the light emitters 1044 emitimage light with a broad angular emission profile 1046. The image lightpropagates through the array 1300 of light collimators, which reducesthe angular emission profile to the narrowed angular emission profile1047.

In addition, the array of 1300 of light collimators is configured toredirect the image light (image light 1032 a, 1032 b, 1032 c) such thatthe image light is incident on the projection optics 1070 at angleswhich cause the projection optics 1070 to output the image light suchthat the image light propagates to the appropriate in-coupling opticalelement 1022 a, 1022 b, 1022 c. For example, the 1300 array of lightcollimators is preferably configured to: direct the image light 1032 asuch that it propagates through the projection optics 1070 and isincident on the in-coupling optical element 1022 a; direct the imagelight 1032 b such that it propagates through the projection optics 1070and is incident on the in-coupling optical element 1022 b; and directthe image light 1032 c such that it propagates through the projectionoptics 1070 and is incident on the in-coupling optical element 1022 c.

Since different light emitters 1044 may emit light of differentwavelengths and may need to be redirected into different directions toreach the appropriate in-coupling optical element, in some embodiments,the light collimators associated with different light emitters 1044 mayhave different physical parameters (e.g., different pitches, differentwidths, etc.). Advantageously, the use of flat nano-lenses as lightcollimators facilitates the formation of light collimators which vary inphysical properties across the array 1300 of light collimators. As notedherein, the nano-lenses may be formed using patterning and depositionprocesses, which facilitates the formation of structures with differentpitches, widths, etc. across a substrate.

With reference again to FIG. 24A, it will be appreciated that theillustrated display system shows a single emissive micro-display andomits an optical combiner 1050 (FIGS. 11A and 12-13B). In embodimentsutilizing an optical combiner 1050, the reflective surfaces 1052, 1054(FIGS. 11A, 12-13B, and 30B) in the optical combiner 1050 are preferablyspecular reflectors, and light from the light emitters 1044 would beexpected to retain their large angular emission profiles after beingreflected from the reflective surfaces 1052, 1054. Thus, the problemswith wasted light shown in FIG. 24A are similarly present when anoptical combiner 1050 is utilized.

With reference now to FIG. 30A, an example of a wearable display systemwith an emissive micro-display and an associated array of lightcollimators is illustrated. FIG. 30A shows additional details regardingthe interplay between the light emitters 1044, the light collimators1302, and the in-coupling optical elements of the eyepiece 1020. Thedisplay system includes a micro-display 1030 b, which may be afull-color micro-display in some embodiments. In some other embodiments,the micro-display 1030 b may be a monochrome micro-display andadditional monochrome micro-displays (not shown) may be provided atdifferent faces of the optional optical combiner 1050 (as shown in FIG.30C).

With continued reference to FIG. 30A, the micro-display 1030 b includesan array of light emitters 1044, each of which emits light with a wideangular emission profile (e.g., a Lambertian angular emission profile).Each light emitter 1044 has an associated, dedicated light collimator1302 which effectively narrows the angular emission profile to anarrowed angular remission profile 1047. Light beams 1032 b with thenarrowed angular emission profiles pass through the projection optics1070, which projects or converges those light beams onto the in-couplingoptical element 1022 b. It will be appreciated that the light beams 1032b have a certain cross-sectional shape and size 1047 a. In someembodiments, the in-coupling optical element 1022 b has a size and shapewhich substantially matches or is larger than the cross-sectional shapeand size of the light beam 1032 b, when that beam 1032 b is incident onthat in-coupling optical element 1022 b. Thus, in some embodiments, thesize and shape of the in-coupling optical element 1022 b may be selectedbased upon the cross-sectional size and shape of the light beam 1032 bwhen incident on the in-coupling optical element 1022 b. In some otherembodiments, other factors (re-bounce mitigation, or the angles or fieldof view supported by the in-coupling optical elements 1022 b) may beutilized to determine the size and shape of the in-coupling opticalelement 1022 b, and the light collimator 1302 may be configured (e.g.,sized and shaped) to provide the light beam 1032 b with an appropriatelysized and shaped cross-section, which is preferably fully or nearlyfully encompassed by the size and shape of the in-coupling opticalelement 1022 b. In some embodiments, physical parameters for the lightcollimator 1302 and the in-coupling optical element 1022 b may bemutually modified to provide highly efficient light utilization inconjunction with other desired functionality (e.g., re-bouncemitigation, support for the desired fields of view, etc.).Advantageously, the above-noted light collimation provided by the lightcollimator 1302, and matching of the cross-sectional size and shape ofthe light beam 1032 b with the size and shape of the in-coupling opticalelement 1022 b allows the in-coupling optical element 1022 b to capturea large percentage of the incident light beam 1032 b. The in-coupledlight then propagates through the waveguide 1020 b and is out-coupled tothe eye 210.

As illustrated, the micro-display 1030 b may comprise an array 1042 oflight emitters 1044, each surrounded by non-light-emitting areas 1045having a total width 1045 w. In addition, the light emitters 1044 have awidth W and a pitch P. In arrays in which the light emitters 1044 areregularly spaced, each light emitter 1044 and surrounding area 1045effectively forms a unit cell having the width 1045 w, which may beequal to the pitch P.

In some embodiments, the light collimators 1302 are micro-lensesdisposed directly on and surrounding associated light emitters 1044. Insome embodiments, the width of the micro-lenses 1302 is equal to 1045 w,such that neighboring micro-lenses 1302 nearly contact or directlycontact one another. It will be appreciated that light from the lightemitters 1044 may fill the associated micro-lens 1302, effectivelymagnifying the area encompassed by the light emitter 1044.Advantageously, such a configuration reduces the perceptibility of theareas 1045 which do not emit light and may otherwise be visible as darkspaces to a user. However, because micro-lens 1302 effectively magnifiesthe associated light emitter 1044 such that it extends across the entirearea of the micro-lens 1302, the areas 1045 may be masked.

With continued reference to FIG. 30A, the relative sizes of the lightemitters 1044 and light collimators 1302 may be selected such that lightfrom the light emitters 1044 fills the associated light collimators1302. For example, the light emitters 1044 may be spaced sufficientlyfar apart such that micro-lens collimators 1302 having the desiredcurvature may be formed extending over individual ones of the lightemitters 1044. In addition, as noted above, the size and shape of theintra-coupling optical element 1022 b is preferably selected such thatit matches or exceeds the cross-sectional shape and size of the lightbeam 1032 b when incident on that in-coupling optical element 1022 b.Consequently, in some embodiments, a width 1025 of the in-couplingoptical element 1022 b is equal to or greater than the width of themicro-lens 1302 (which may have a width equal to 1045 w or P).Preferably, the width 1025 is greater than the width of the micro-lens1302, or 1045 w or P, to account for some spread in the light beam 1032b. As discussed herein, the width 1025 may also be selected to mitigaterebounce and may be shorter than the length (which is orthogonal to thewidth) of the in-coupling optical element 1022 b. In some embodiments,the width 1025 may extend along the same axis as the direction ofpropagation of incoupled light 1032 b through the waveguide 1020 bbefore being out-coupled for propagation to the eye 210.

With reference now to FIG. 30B, an example of a light projection system1010 with multiple emissive micro-displays 1030 a, 1030 b, 1030 c, andassociated arrays 1300 a, 1300 b, 1300 c of light collimators,respectively, is illustrated. The angular emission profiles of lightemitted by the micro-displays 1030 a, 1030 b, 1030 c are narrowed by thelight collimator arrays 1300 a, 1300 b, 1300 c, thereby facilitating thecollection of a large percentage of the emitted light by the projectionoptics 1070 after the light propagates through the optical combiner1050. The projection optics 1070 then directs the light to an eyepiecesuch as the eyepiece 1020 (e.g., FIGS. 11A and 12-14) (not shown).

FIG. 30C illustrates an example of a wearable display system withmultiple emissive micro-displays 1030 a, 1030 b, 1030 c, each with anassociated array 1300 a, 1300 b, 1300 c, respectively, of lightcollimators. The illustrated display system includes a plurality ofmicro-displays 1030 a, 1030 b, 1030 c for emitting light with imageinformation. As illustrated, the micro-displays 1030 a, 1030 b, 1030 cmay be micro-LED panels. In some embodiments, the micro-displays may bemonochrome micro-LED panels, each configured to emit a differentcomponent color. For example, the micro-display 1030 a may be configuredto emit light 1032 a which is red, the micro-display 1030 b may beconfigured to emit light 1032 b which is green, and the micro-display1030 c may be configured to emit light 1032 c which is blue.

Each micro-display 1030 a, 1030 b, 1030 c may have an associated array1300 a, 1300 b, 1300 c, respectively, of light collimators. The lightcollimators narrow the angular emission profile of light 1032 a, 1032 b,1032 c from light emitters of the associated micro-display. In someembodiments, individual light emitters have a dedicated associated lightcollimator (as shown in FIG. 30A).

With continued reference to FIG. 30C, the arrays 1300 a, 1300 b, 1300 cof light collimators are between the associated micro-displays 1030 a,1030 b, 1030 c and the optical combiner 1050, which may be an X-cube. Asillustrated, the optical combiner 1050 has internal reflective surfaces1052, 1054 for reflecting incident light out of an output face of theoptical combiner. In addition to narrowing the angular emission profileof incident light, the arrays 1300 a, 1300 c of light collimators may beconfigured to redirect light from associated micro-displays 1030 a, 1030c such that the light strikes the internal reflective surfaces 1052,1054 of the optical combiner 1050 at angles appropriate to propagatetowards the associated light in-coupling optical elements 1022 a, 1022c, respectively. In some embodiments, in order to redirect light in aparticular direction, the arrays 1300 a, 1300 c of light collimators maycomprise micro-lens or reflective wells, which may be asymmetricaland/or the light emitters may be disposed off-center relative to themicro-lens or reflective wells, as disclosed herein.

With continued reference to FIG. 30C, projection optics 1070 (e.g.,projection lens) is disposed at the output face of the optical combiner1050 to receive image light exiting from that optical combiner. Theprojection optics 1070 may comprise lenses configured to converge orfocus image light onto the eyepiece 1020. As illustrated, the eyepiece1020 may comprise a plurality of waveguides, each of which is configuredto in-couple and out-couple light of a particular color. For example,waveguide 1020 a may be configured to receive red light 1032 a from themicro-display 1030 a, waveguide 1020 b may be configured to receivegreen light 1032 b from the micro-display 1030 b, and waveguide 1020 cmay be configured to receive blue light 1032 c from the micro-display1030 c. Each waveguide 1020 a, 1020 b, 1020 c has an associated lightin-coupling optical elements 1022 a, 1022 b, 1022 c, respectively, forin coupling light therein. In addition, as discussed herein, thewaveguides 1020 a, 1020 b, 1020 c may correspond to the waveguides 670,680, 690, respectively, of FIG. 9B and may each have associatedorthogonal pupil expanders (OPE's) and exit pupil expanders (EPE's),which ultimately out-couple the light 1032 a, 1032 b, 1032 c to a user.

As discussed herein, the wearable display system incorporatingmicro-displays is preferably configured to output light with differentamounts of wavefront divergence, to provide comfortableaccommodation-vergence matching for the user. These different amounts ofwavefront divergence may be achieved using out-coupling optical elementswith different optical powers. As discussed herein, the out-couplingoptical elements may be present on or in waveguides of an eyepiece suchas the eyepiece 1020 (e.g., FIGS. 11A and 12-14). In some embodiments,lenses may be utilized to augment the wavefront divergence provided bythe out-couple optical elements or may be used to provide the desiredwavefront divergence in configurations where the out-couple opticalelements are configured to output collimated light.

FIGS. 31A and 31B illustrate examples of eyepieces 1020 having lens forvarying the wavefront divergence of light to a viewer. FIG. 31Aillustrates an eyepiece 1020 having a waveguide structure 1032. In someembodiments, as discussed herein, light of all component colors may bein-coupled into a single waveguide, such that the waveguide structure1032 includes only the single waveguide. This advantageously providesfor a compact eyepiece. In some other embodiments, the waveguidestructure 1032 may be understood to include a plurality of waveguides(e.g., the waveguides 1032 a, 1032 b, 1032 c of FIGS. 11A and 12-13A),each of which may be configured to relay light of a single componentcolor to a user's eye.

In some embodiments, the variable focus lens elements 1530, 1540 may bedisposed on either side of the waveguide structure 1032. The variablefocus lens elements 1530, 1540 may be in the path of image light fromthe waveguide structure 1032 to the eye 210, and also in the path oflight from the ambient environment through the waveguide structure 10032 to the eye 210. The variable focus optical element 1530 may modulatethe wavefront divergence of image light outputted by the waveguidestructure 1032 to the eye 210. It will be appreciated that the variablefocus optical element 1530 may have optical power which may distort theeye 210's view of the world. Consequently, in some embodiments, a secondvariable focus optical element 1540 may be provided on the world side ofthe waveguide structure 1032. The second variable focus optical element1540 may provide optical power opposite to that of the variable focusoptical element 1530 (or opposite to the net optical power of theoptical element 1530 and the waveguide structure 1032, where thewaveguide structure 1032 has optical power), so that the net opticalpower of the variable focus lens elements 1530, 1540 and the waveguidestructure 1032 is substantially zero.

Preferably, the optical power of the variable focus lens elements 1530,1540 may be dynamically altered, for example, by applying an electricalsignal thereto. In some embodiments, the variable focus lens elements1530, 1540 may comprise a transmissive optical element such as a dynamiclens (e.g., a liquid crystal lens, an electro-active lens, aconventional refractive lens with moving elements, amechanical-deformation-based lens, an electrowetting lens, anelastomeric lens, or a plurality of fluids with different refractiveindices). By altering the variable focus lens elements' shape,refractive index, or other characteristics, the wavefront of incidentlight may be changed. In some embodiments, the variable focus lenselements 1530, 1540 may comprise a layer of liquid crystal sandwichedbetween two substrates. The substrates may comprise an opticallytransmissive material such as glass, plastic, acrylic, etc.

In some embodiments, in addition or as alternative to providing variableamounts of wavefront divergence for placing virtual content on differentdepth planes, the variable focus lens elements 1530, 1540 and waveguidestructure 1032 may advantageously provide a net optical power equal tothe user's prescription optical power for corrective lenses. Thus, theeyepiece 1020 may serve as a substitute for lenses used to correct forrefractive errors, including myopia, hyperopia, presbyopia, andastigmatism. Further details regarding the use of variable focus lenselements as substitutes for corrective lenses may be found in U.S.application Ser. No. 15/481,255, filed Apr. 6, 2017, the entiredisclosure of which is incorporated by reference herein.

With reference now to FIG. 31B, in some embodiments, the eyepiece 1020may include static, rather than variable, lens elements. As with FIG.31B, the waveguide structure 1032 may include a single waveguide (e.g.,which may relay light of different colors) or a plurality of waveguides(e.g., each of which may relay light of a single component color).Similarly, the waveguide structure 1034 may include a single waveguide(e.g., which may relay light of different colors) or a plurality ofwaveguides (e.g., each of which may relay light of a single componentcolor). The one or both of the waveguide structures 1032, 1034 may haveoptical power and may output light with particular amounts of wavefrontdivergence, or may simply output collimated light.

With continued reference to FIG. 31B, the eyepiece 1020 may includestatic lens elements 1532, 1534, 1542 in some embodiments. Each of theselens elements are disposed in the path of light from the ambientenvironment through waveguide structures 1032, 1034 into the eye 210. Inaddition, the lens element 1532 is between a waveguide structure 1003 2and the eye 210. The lens element 1532 modifies a wavefront divergenceof light outputted by the waveguide structure 1032 to the eye 210.

The lens element 1534 modifies a wavefront divergence of light outputtedby the waveguide structure 1034 to the eye 210. It will be appreciatedthat the light from the waveguide structure 1034 also passes through thelens element 1532. Thus, the wavefront divergence of light outputted bythe waveguide structure 1034 is modified by both the lens element 1534and the lens element 1532 (and the waveguide structure 1032 in caseswhere the waveguide structure 1003 2 has optical power). In someembodiments, the lens elements 1532, 1534 and the waveguide structure1032 provide a particular net optical power for light outputted from thewaveguide structure 1034.

The illustrated embodiment provides two different levels of wavefrontdivergence, one for light outputted from the waveguide structure 1032and a second for light outputted by a waveguide structure 1034. As aresult, virtual objects may be placed on two different depth planes,corresponding to the different levels of wavefront divergence. In someembodiments, an additional level of wavefront divergence and, thus, anadditional depth plane may be provided by adding an additional waveguidestructure between lens element 1532 and the eye 210, with an additionallens element between the additional waveguide structure and the eye 210.Further levels of wavefront divergence may be similarly added, by addingfurther waveguide structures and lens elements.

With continued reference to FIG. 31B, it will be appreciated that thelens elements 1532, 1534 and the waveguide structures 1032, 1034 providea net optical power that may distort the users view of the world. As aresult, lens element 1542 may be used to counter the optical power anddistortion of ambient light. In some embodiments, the optical power ofthe lens element 1542 is set to negate the aggregate optical powerprovided by the lens elements 1532, 1534 and the waveguide structures1032, 1034. In some other embodiments, the net optical power of the lenselement 1542; the lens elements 1532, 1534; and the waveguide structures1032, 1034 is equal to a user's prescription optical power forcorrective lenses.

As discussed herein, emissive micro-displays may provide very high framerate operation. As examples, emissive micro-displays may be capable ofproviding frame rates of 120 Hz or more, or 240 Hz or more, or evenhigher frame rates. Due in part to the high frame rate capabilities ofsuch emissive micro-displays, a wearable system may be provided with oneor more emissive micro-displays that each generate distinct image framesfor both left and right eyepieces of the wearable system, along withtime-synchronized routing of the image frames to the appropriate one ofthe left and right eyepieces. Advantageously, the emissivemicro-displays may be capable of frame rates that are at least multiplesof the frame rate at which virtual content is presented to a user. As aresult, the emissive micro-display (or one or more micro-displays wherea light projection system utilizes multiple micro-displays) may havesufficient surplus frame rate capability that it may display imageframes for multiple eyepieces without impacting the rate at which imageframes are presented by any individual eyepiece.

As an example, one or more micro-displays with frame rates of 120 Hz ormore may be configured to provide left-eye image frames at 60 Hz to aleft eyepiece, while also providing right-eye image frames at 60 Hz to aright eyepiece. The micro-displays may temporally interleave the displayof left-eye and right-eye image frames, which may also be referred to asleft-eye and right-eye images, respectively. As an example, themicro-displays may alternate (e.g., in a time-multiplexing scheme)between generating a left-eye image frame that is routed to a lefteyepiece and a right-eye image frame that is routed to a right eyepiece.In some embodiments, the micro-displays may display multiple left-eyeimage frames and/or multiple right-eye image frames in succession beforedisplaying image frames for the other eye. As discussed herein, in someembodiments, image frames for any individual eye are provided to theuser at a frame rate equal to or higher than the frame ratecorresponding to the flicker fusion threshold of the user. For example,the frame rate for each of the left-eye or right-eye pieces may be 60 Hzor more, or 120 Hz or more; and, as a result, the frame rate provided bythe light projection system 1010 may be 120 Hz or more, or 240 Hz ormore in some embodiments.

With reference now to FIG. 32, an example is illustrated of a wearabledisplay system with a light projection system 1010 having one or moreemissive micro-displays, and an optical router 3201 for selectivelydirecting light to left and right eyepieces 1020L and 1020R,respectively. The wearable display system may be a head-mounted displaysystem, as discussed herein. The light projection system 1010 is commonto and configured to generate image frames for both the left eyepiece1020L and the right eyepiece 1020R. The light projection system 1010 maybe any of the light projection systems disclosed herein. In someembodiments, the light projection system 1010 may include one or moreof, for example, micro-displays (e.g. one or more of micro-displays 1030a, 1030 b, 1030 c), an optical combiner (e.g. optical combiner 1050),light redirecting structures (e.g., light redirecting structures 1080 a,1080 b), light collimating arrays (e.g. light collimating arrays 1300)projection optics (e.g., projection optics 1070), etc., as discussedherein with reference to, e.g., FIGS. 10A-14 and 24B-30C.

With continued reference to FIG. 32, time-multiplexed left and right eyeimages are generated by the light projection system 1010 (e.g., usingone or more emissive micro-displays) with image light 1032LR and thende-multiplexed using the optical router 3201, which routes image light1032L for left-eye images to left eyepiece 1020L and image light 1032Rfor right eye images to right eyepiece 1020R. Control electronics 3200may be operatively coupled and in communication with the lightprojection system 1010 and the optical router 3201. The controlelectronics 3200 may be configured to receive information from the lightprojection system 1010 and/or the optical router 3201 (e.g. regardingtheir operational status) and may send commands to control theoperations of the light projection system 1010 and/or the optical router3201. In some embodiments, the control electronics 3200 may beconfigured to synchronize the operation of the optical router 3201 tothe operation of the light projection system 1010 (e.g., so that theoptical router 3201 properly de-multiplexes the time-multiplexed imagesfrom the light projection system 1010). The control electronics 3200 mayinclude programming (e.g., instructions stored in a non-transitorymedium) to perform the various actions disclosed herein, includingregulating the generation of images by one or more emissivemicro-displays and regulating the operation of the optical router 3201.In some embodiments, the control electronics 3200 may be part of thelocal processing and data module 140 (FIG. 9E) and/or the remoteprocessing module 150 and remote data repository 160.

It will be appreciated that the left and right eyepieces 1020L and 1020Rare similar to the eyepieces 1020 disclosed herein (see e.g., FIGS. 11A,12-23C, 29-30A, and 30C-31B and the related description), the letters“L” and “R” designating the eyepieces as being left and right eyepieces,respectively. For example, the left and right eyepieces 1020L and 1020Rmay include a single waveguide, or one or more waveguides arranged in astack, as discussed herein. In some embodiments, the left and righteyepieces 1020L and 1020R may include in-coupling optical elements andout-coupling optical elements, as discussed herein. In some embodiments,where the left and right eyepieces 1020L and 1020R include a stack ofwaveguides, the in-coupling optical elements of different waveguides mayoverlap and be in the same path of light from the light projectionsystem 1010, as discussed herein. In some embodiments, at least somein-coupling optical elements may be laterally displaced (as seen in atop-down view of a major surface of the eyepiece), such that lightstriking the in-coupling optical element of one waveguide does notimpinge on the in-coupling optical element of an underlying waveguide,as discussed herein. In some embodiments, one or more optical filtersmay be disposed between waveguides of a stack of waveguides to reducethe presence of unintentionally in-coupled light within waveguides, asdiscussed herein.

The optical router 3201 may be configured to route image light todifferent (e.g., left and right) eyepieces by outputting the image lightalong different paths (e.g. in different directions) and/or by changingone or more properties of the light such that the light interactsdifferently with optical structures, outside of the optical router 3201,to redirect the light into different eyepieces. In some embodiments, thelight projection system 1010 may provide image light forming left-eyeand right-eye image frames with different polarization states,respectively. The optical router 3201 may then utilize polarizationsensitive optical structures to selectively redirect light of aparticular polarization (for image frames of a particular eyepiece) in adesired direction and/or into a desired waveguide.

In some embodiments, the optical router 3201 includes a polarizer thatis configured to receive image light 1032LR from the light projectionsystem 1010 and to output a portion of the image light 1032LR having afirst polarization state, while blocking light of a second polarizationstate. Thus, light (having multiple polarization states) from the lightprojection system 1010 is effectively converted into polarized lighthaving a single polarization state. The optical router 3201 may furtherinclude a selectively activated polarization rotator that receives thepolarized light and either transmits the received light without a changein polarization state, or changes the polarization state of thepolarized light. In some embodiments, the optical router 3201 mayinclude a polarization sensitive reflector (e.g., a polarization beamsplitter) that directs image light of a first polarization state towardsa first eyepiece (e.g., a left eyepiece 1020L) and that substantiallyallows light of a second polarization to pass without being reflected.The light of the second polarization state may then reach a secondeyepiece (e.g., right eyepiece 1020R). In some embodiments, the opticalrouter 3201 may include a second reflector, which may or may not bepolarization sensitive and which reflects the light of the secondpolarization state towards the second eyepiece (e.g., right eyepiece1020R), as discussed below regarding FIG. 33.

In some embodiments, the optical router 3201 may be configured to simplyoutput image light 1032LR of different polarization states along acommon light path. The eyepieces 1020L and 1020R may include opticalstructures (e.g., in-coupling optical elements) which receive the imagelight 1032LR. Different eyepieces may include in-coupling opticalelements to in-couple different polarization states. Thus, the eyepieceinto which the image light is in-coupled may depend upon thepolarization state of the incident light, as discussed below regardingFIG. 34.

With reference now to FIG. 33, an example as illustrated of a wearabledisplay system having an optical router 3201 that includes apolarization-sensitive reflective structure 3306 for selectivelydirecting images along different paths to left and right eyepieces 1020Land 1020R, respectively. As noted therein, a light projection system1010 generates image light 1032LR which forms left and right-eye imageframes that are selectively polarized based on whether a given imageframe is a left-eye or a right-eye image frame. After being polarized,image light 1032L for left-eye image frames are routed to left eyepiece1020L and image light 1032R for right-eye image frames are routed toright-eyepiece 1020R by the polarization-sensitive reflective structure3306, depending upon the selectively-applied polarization for a givenimage frame. In some embodiments, the polarization-sensitive reflectivestructure 3306 is a polarizing beam splitter (PBS). It will beappreciated that polarization-sensitive features selectively act onlight having a particular polarization while being substantiallytransparent to light having a different polarization.

In some embodiments, polarizer 3302 may linearly polarize light passingthrough the polarizer 3302 and preferably provides a polarizationorientation that is aligned with polarization rotator 3304 (e.g., as theperformance of the polarization rotator 3304 may be improved when itreceives light polarized with a particular orientation).

The polarization rotator 3304 may be selectively electrically-switchablesuch that, in a first state, the polarization rotator 3304 outputs lighthaving a first polarization state and such that, in a second state, thepolarization rotator 3304 outputs light having a second polarizationstate that is orthogonal to the first polarization state. The controlelectronics 3200 may control the state of the polarization rotator 3304and may synchronize the state of the polarization rotator 3304 with theoutput of image light 1032LR for left or right-eye images from the lightprojection system 1010. In some embodiments, the polarization rotator3304 may be configured to preserve the polarization of passing polarizedlight, when configured in the first state, and may be configured torotate the polarization of passing polarized light by 90°, whenconfigured in the second state. In some embodiments, the polarizationrotator 3304 may rotate the polarization direction of light in both itsfirst and second states. The polarization rotator 3304 may, as anexample, include a switchable half-wave plate (HWP).

The polarization rotator 3304 is configured to change states at asufficiently high rate to match the frame rate of images generated bythe light projection system 1010. In some embodiments, the polarizationrotator 3304 is configured to change states at a rate of at least doublethe frame rate of images provided to a single eye of the user.Additionally, the polarization rotator 3304 may be configured to switchbetween first and second states in sync with the light projection system1010, such that light for left-eye images generated by the lightprojection system 1010 pass through the polarization rotator 3304 whileit is in a first state and such that light for right-eye imagesgenerated by the light projection system 1010 pass through thepolarization rotator 3304 while it is in a second state. In this manner,the polarization rotator 3304 may output image light 1032L for imagesfor the left eyepiece 1020L at a desired frame rate (which may be 30 Hz,45 Hz, 60 Hz, or greater than 60 Hz) and also output image light 1032Rfor images for the right eyepiece 1020R at a desired frame rate (whichmay be 30 Hz, 45 Hz, 60 Hz, or greater than 60 Hz).

After passing through the polarization rotator 3304, the polarized lightpropagates through an optical component that redirects the polarizedimage light 1032L or 1032R to either the left eyepiece 1020L or theright eyepiece 1020R, for example, depending on the polarization of theimage light. As an example, the polarized light from the polarizationrotator 3304 may be passed through a polarization-sensitive reflectivestructure 3306 (e.g. a polarization beam splitter), which may include apolarization-sensitive mirror 3308 that reflects light having a firstpolarization (e.g., the polarization imparted by polarizer 3302 androtator 3304 for light 1032L associated with left-eye images) andthereby redirects the light towards one or more in-coupling opticalelements 1022L for the left eyepiece 1020L. The polarization-sensitivemirror 3308 may be transparent to light having a second polarization(e.g., the orthogonal polarization imparted by rotator 3304 for light1032R associated with right-eye images) such that the light having thesecond polarization passes to mirror 3310, which in turn redirects thelight towards one or more in-coupling optical elements 1022R associatedwith the right eyepiece 1020R. It will be appreciated that the mirror3310 may simply be a reflective surface that reflects light of allpolarizations. In some embodiments, the mirror 3310 may be apolarization-sensitive mirror, which may have advantages for improvingthe selectivity of light in-coupled to the right eyepiece 1020R. In someembodiments, the in-coupling optical elements 1022L and 1022R may bepolarization sensitive, which may also have advantages for preventingthe unintentional in-coupling of light of undesired polarizations (e.g.,to prevent the in-coupling of light for image frames intended for theother eyepiece). In some embodiments, the in-coupling optical elements1022L, 1022R may be diffractive gratings. In some embodiments, thein-coupling optical elements 1022L, 1022R may be a metasurface and/orliquid crystal gratings.

Thus, distinct left and right-eye images generated by the lightprojection system 1010 may be provided to the corresponding left andright-eye eyepieces 1020L, 1020R by outputting light from the opticalrouter 3201 to the corresponding eyepiece.

With reference now to FIG. 34, in some embodiments, the optical router3201 may be configured to simply modify a polarization of the light1032LR to output light 1032L and 1032R along a common optical path. Thelight 1032L and 1032R have different polarization states that allowdownstream polarization-sensitive in-coupling optical elements toselectively in-couple light of a desired polarization into thecorresponding left or right eyepiece. FIG. 34 illustrates an example ofa wearable display system with an optical router 3201 that switchespolarization states of incident image light, and left and righteyepieces 1020L, 1020R having in-coupling optical elements 1022L′,1022R′ that selectively in-couple light of different polarizationstates. In some embodiments, the in-coupling optical elements 1022L′,1022R′ may be diffractive gratings. In some embodiments, the in-couplingoptical elements 1022L′, 1022R′ may be a metasurface and/or liquidcrystal gratings.

As illustrated, a portion of the left and right eyepieces 1020L, 1020Rmay overlap such that the left-eye in-coupling optical elements 1022Lare substantially aligned with the right-eye in-coupling opticalelements 1022R, so that both in-coupling optical elements are in thesame optical path of light outputted by the optical router 3201. As anexample, the in-coupling optical elements 1022L and 1022R may be locatedat approximately the midway point between a user's left and right eyesor may, if desired, be located towards one side of the midway point.

The in-coupling optical elements of at least one eyepiece (e.g., theleft or right eyepiece) may be polarization-sensitive. Preferably, themost upstream in-coupling optical element (the first of the in-couplingoptical elements that receives light from the optical router 3201) ispolarization-sensitive. FIG. 34 illustrates an example in which theleft-eye in-coupling optical element 1022L is polarization-sensitive and“upstream” of the right-eye in-coupling optical element 1022R. In suchembodiments, the left-eye in-coupling optical element 1022L may beconfigured to in-couple light having a first polarization into the lefteyepiece 1020L and may be configured to pass light having a secondorthogonal polarization to the right-eye in-coupling optical elements1022R. The right-eye in-coupling optical element 1022R may then beconfigured to in-couple the remaining light (e.g., the light notin-coupled by elements 1022L) into the right eyepiece 1020R.

In some embodiments, the left-eye in-coupling optical element 1022L maynot in-couple all image light 1032L of the first polarization state,such that some of this image light 1032L may propagate to the right-eyein-coupling optical element 1022R. Consequently, it may be advantageousto prevent in-coupling of this image light 1032L into the right eyepiece1020R. In some embodiments, the right-eye in-coupling optical elements1022R may also be polarization-sensitive, such that the elements 1022Rselectively in-couple light 1022R having the second polarization stateto the exclusion of light 1022L having the first polarization state. Insome embodiments, an additional polarizer, which may be referred to as aclean-up polarizer, can be positioned between the left-eye in-couplingoptical elements 1022L and the right-eye in-coupling optical element1022R. The clean-up polarizer may help prevent cross-talk by preventingthe propagation of light 1032L to the right-eye in-coupling opticalelement 1022R.

With reference to FIGS. 32-34, it will be appreciated that the opticalrouter 3201 may be a mechanically switchable device that directs light1032LR to the appropriate one of the left-eye in-coupling opticalelements 1022L or the right-eye in-coupling optical element 1022R. Forexample, the optical router 3201 may be a mirror configured to assume: afirst orientation that reflects light to one of the right or lefteyepieces 1022L, 1022R; and a second orientation that reflects light tothe other right or left eyepieces 1022L, 1022R. In some embodiments, themirror is a MEMS mirror. In some embodiments, the mirror is a scanningmirror having a mirror attached to an actuator that moves, for example,rotates, the mirror.

As discussed herein, emissive displays such as micro-displays mayprovide relatively high brightness, which may compensate for any lossesassociated with polarizing light from the light projection system 1010and passing the polarized light through polarization-sensitivecomponents such as the polarization beam splitter 3310 andpolarization-sensitive in-coupling optical elements such as elements1022L′ and/or 1022R′. Additionally, in systems that use switchablepolarization to route left and right images, reliability and performancemay be improved over some mechanical optical routing systems, since suchpolarization-based systems may be less sensitive to mechanicaldisturbances than mechanical systems.

With reference now to FIGS. 11A-34, it will be appreciated that theillustrated components of any of the wearable display systems may besupported on the frame 80 (FIG. 9E). As such, these components may eachbe effectively mounted on the head of a user 90 as part of a wearabledisplay system.

Various example embodiments of the invention are described herein.Reference is made to these examples in a non-limiting sense. They areprovided to illustrate more broadly applicable aspects of the invention.Various changes may be made to the invention described and equivalentsmay be substituted without departing from the spirit and scope of theinvention.

For example, while advantageously utilized with AR displays that provideimages across multiple depth planes, the augmented reality contentdisclosed herein may also be displayed by systems that provide images ona single depth plane.

In addition, many modifications may be made to adapt a particularsituation, material, composition of matter, process, process act, orstep(s) to the objective(s), spirit, or scope of the present invention.Further, as will be appreciated by those with skill in the art that eachof the individual variations described and illustrated herein hasdiscrete components and features which may be readily separated from orcombined with the features of any of the other several embodimentswithout departing from the scope or spirit of the present inventions.All such modifications are intended to be within the scope of claimsassociated with this disclosure.

The invention includes methods that may be performed using the subjectdevices. The methods may comprise the act of providing such a suitabledevice. Such provision may be performed by the user. In other words, the“providing” act merely requires the user obtain, access, approach,position, set-up, activate, power-up or otherwise act to provide therequisite device in the subject method. Methods recited herein may becarried out in any order of the recited events that is logicallypossible, as well as in the recited order of events.

In addition, it will be appreciated that each of the processes, methods,and algorithms described herein and/or depicted in the figures may beembodied in, and fully or partially automated by, code modules executedby one or more physical computing systems, hardware computer processors,application-specific circuitry, and/or electronic hardware configured toexecute specific and particular computer instructions. For example,computing systems may include general purpose computers (e.g., servers)programmed with specific computer instructions or special purposecomputers, special purpose circuitry, and so forth. A code module may becompiled and linked into an executable program, installed in a dynamiclink library, or may be written in an interpreted programming language.In some embodiments, particular operations and methods may be performedby circuitry that is specific to a given function.

Further, certain embodiments of the functionality of the presentdisclosure are sufficiently mathematically, computationally, ortechnically complex that application-specific hardware or one or morephysical computing devices (utilizing appropriate specialized executableinstructions) may be necessary to perform the functionality, forexample, due to the volume or complexity of the calculations involved orto provide results substantially in real-time. For example, a video mayinclude many frames, with each frame having millions of pixels, andspecifically programmed computer hardware is necessary to process thevideo data to provide a desired image processing task or application ina commercially reasonable amount of time.

Code modules or any type of data may be stored on any type ofnon-transitory computer-readable medium, such as physical computerstorage including hard drives, solid state memory, random access memory(RAM), read only memory (ROM), optical disc, volatile or non-volatilestorage, combinations of the same and/or the like. In some embodiments,the non-transitory computer-readable medium may be part of one or moreof the local processing and data module (140), the remote processingmodule (150), and remote data repository (160). The methods and modules(or data) may also be transmitted as generated data signals (e.g., aspart of a carrier wave or other analog or digital propagated signal) ona variety of computer-readable transmission mediums, includingwireless-based and wired/cable-based mediums, and may take a variety offorms (e.g., as part of a single or multiplexed analog signal, or asmultiple discrete digital packets or frames). The results of thedisclosed processes or process steps may be stored, persistently orotherwise, in any type of non-transitory, tangible computer storage ormay be communicated via a computer-readable transmission medium.

Any processes, blocks, states, steps, or functionalities describedherein and/or depicted in the attached figures should be understood aspotentially representing code modules, segments, or portions of codewhich include one or more executable instructions for implementingspecific functions (e.g., logical or arithmetical) or steps in theprocess. The various processes, blocks, states, steps, orfunctionalities may be combined, rearranged, added to, deleted from,modified, or otherwise changed from the illustrative examples providedherein. In some embodiments, additional or different computing systemsor code modules may perform some or all of the functionalities describedherein. The methods and processes described herein are also not limitedto any particular sequence, and the blocks, steps, or states relatingthereto may be performed in other sequences that are appropriate, forexample, in serial, in parallel, or in some other manner. Tasks orevents may be added to or removed from the disclosed exampleembodiments. Moreover, the separation of various system components inthe embodiments described herein is for illustrative purposes and shouldnot be understood as requiring such separation in all embodiments. Itshould be understood that the described program components, methods, andsystems may generally be integrated together in a single computerproduct or packaged into multiple computer products.

Example aspects of the invention, together with details regardingmaterial selection and manufacture have been set forth above. As forother details of the present invention, these may be appreciated inconnection with the above-referenced patents and publications as well asgenerally known or appreciated by those with skill in the art. The samemay hold true with respect to method-based aspects of the invention interms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference toseveral examples optionally incorporating various features, theinvention is not to be limited to that which is described or indicatedas contemplated with respect to each variation of the invention. Variouschanges may be made to the invention described and equivalents (whetherrecited herein or not included for the sake of some brevity) may besubstituted without departing from the spirit and scope of theinvention. In addition, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin claims associated hereto, the singular forms “a,” “an,” “said,” and“the” include plural referents unless the specifically stated otherwise.In other words, use of the articles allow for “at least one” of thesubject item in the description above as well as claims associated withthis disclosure. It is further noted that such claims may be drafted toexclude any optional element. As such, this statement is intended toserve as antecedent basis for use of such exclusive terminology as“solely,” “only” and the like in connection with the recitation of claimelements, or use of a “negative” limitation. Without the use of suchexclusive terminology, the term “comprising” in claims associated withthis disclosure shall allow for the inclusion of any additionalelement—irrespective of whether a given number of elements areenumerated in such claims, or the addition of a feature could beregarded as transforming the nature of an element set forth in suchclaims.

Accordingly, the claims are not intended to be limited to theembodiments shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

What is claimed is:
 1. A head-mounted display system comprising: ahead-mountable frame; a light projection system comprising an emissivemicro-display, wherein the light projection system is configured tooutput image light comprising left-eye image light for forming left-eyeimages time-multiplexed with right-eye image light for forming right-eyeimages; a left eyepiece supported by the frame; a right eyepiecesupported by the frame; and an optical router configured to: receive theimage light from the light projection system, and provide, at differenttimes, the left-eye image light to the left eyepiece and the right-eyeimage light to the right eyepiece.
 2. The head-mounted display system ofclaim 1, wherein the optical router comprises: a polarizer configured toreceive the image light and to output the image light with a firstpolarization state; and a switchable polarization rotator configured toreceive the image light with the first polarization state and toselectively change a polarization state of the received image light to asecond polarization state.
 3. The head-mounted display system of claim2, wherein the electrically-switchable polarization rotator comprises aswitchable half-wave plate (HWP).
 4. The head-mounted display system ofclaim 2, further comprising control electronics configured tosynchronize: generation of left-eye image images by the light projectionsystem and routing of the left-eye image light to the left eyepiece bythe optical router; and generation of the right-eye images by the lightprojection system and routing of the right-eye image light to the righteyepiece by the optical router, wherein the electrically-switchablepolarization rotator is synchronized, by the control electronics, withthe light projection system to output left-eye image light with a firstpolarization state and to output right-eye image light with a secondpolarization different from the first polarization state.
 5. Thehead-mounted display system of claim 2, wherein the optical routerfurther comprises a polarization-sensitive reflector configured toreceive the image light from the switchable polarization rotator,wherein the polarization-sensitive reflector is configured to reflectimage light having the first polarization state and transmit image lighthaving the second polarization state.
 6. The head-mounted display systemof claim 5, wherein the polarization-sensitive reflector is configuredto: direct left-eye image light having one of the first and secondpolarization states towards the left eyepiece; and direct right-eyeimage light having the other of the first and second polarization statestowards the right eyepiece.
 7. The head-mounted display system of claim5, wherein the polarization-sensitive reflector comprises a polarizationbeam splitter.
 8. The head-mounted display system of claim 1, whereinthe left eyepiece comprises one or more left-eye waveguides forming aleft-eye waveguide assembly, each left-eye waveguide comprising: aleft-eye in-coupling optical element configured to in-couple image lightinto the left-eye waveguide; and a left-eye out-coupling optical elementconfigured to out-couple in-coupled image light out of the left-eyewaveguide, and the right eyepiece comprises one or more right-eyewaveguides forming a right-eye waveguide assembly, each right-eyewaveguide comprising: a right-eye in-coupling optical element configuredto in-couple image light into the right-eye waveguide; and a right-eyeout-coupling optical element configured to out-couple in-coupled imagelight out of the right-eye waveguide.
 9. The head-mounted display systemof claim 8, wherein the left-eye waveguide assembly is configured tooutput the in-coupled light with variable amounts of wavefrontdivergence corresponding to a plurality of depth planes and wherein theright-eye waveguide assembly is configured to output the out-coupledlight with variable amounts of wavefront divergence corresponding to theplurality of depth planes.
 10. The head-mounted display system of claim8, wherein the left-eye waveguide assembly comprises a first stack ofwaveguides, wherein the right-eye waveguide assembly comprises a secondstack of waveguides, wherein the light projection system is configuredto output light of a plurality of component colors, wherein each of theleft-eye and right-eye waveguide assemblies comprises at least onededicated waveguide for light of each component color.
 11. Thehead-mounted display system of claim 1, wherein the left eyepiececomprises one or more left-eye waveguides, each left-eye waveguidecomprising: a left-eye polarization-sensitive in-coupling opticalelement configured to in-couple light having the first polarizationstate into the left-eye waveguide; and a left-eye out-coupling opticalelement configured to out-couple in-coupled light out of the left-eyewaveguide.
 12. The head-mounted display system of claim 11, wherein theright eyepiece comprises: one or more right-eye waveguides, eachright-eye waveguide comprising: a right-eye polarization-sensitivein-coupling optical element configured to in-couple light having thesecond polarization state into the right-eye waveguide; and a right-eyeout-coupling optical element configured to out-couple in-coupled lightout of the right-eye waveguide.
 13. The head-mounted display of claim12, wherein the left-eye polarization-sensitive in-coupling opticalelement and the right-eye polarization-sensitive in-coupling opticalelement are disposed in a same image light path.
 14. The head-mounteddisplay of claim 13, further comprising a cleanup polarizer disposedbetween the left-eye polarization-sensitive in-coupling optical elementand the right-eye polarization-sensitive in-coupling optical element,wherein the cleanup polarizer is configured to: block light not having apolarization for which the downstream polarization-sensitive in-couplingoptical element is configured sensitive.
 15. The head-mounted displaysystem of claim 1, wherein the emissive micro-display comprises amicro-LED display.
 16. The head-mounted display system of claim 1,further comprising a plurality of emissive micro-displays, wherein eachmicro-LED display is a monochromatic and configured to emit light of acomponent color.
 17. The head-mounted display system of claim 16,further comprising an X-cube prism, wherein each of the emissivemicro-LED displays face a different side of the X-cube prism.
 18. Thehead-mounted display system of claim 17, wherein each micro-LED displaycomprises an array of light emitters, further comprising a plurality ofarrays of light collimators, wherein each micro-display has anassociated array of light collimators, and wherein each array of lightcollimators is configured to capture and reduce an angular emissionprofile of light from the micro-display.
 19. The head-mounted displaysystem of claim 18, wherein the light collimators comprise micro-lenses.20. The head-mounted display system of claim 18, wherein the lightcollimators comprise nano-lenses.